Liquid crystal displays and liquid crystalline media with homeotropic alignment

ABSTRACT

The present invention relates to liquid-crystalline media (LC media) having negative or positive dielectric anisotropy comprising self-aligning mesogens (SAMs) which effect homeotropic (vertical) alignment of the LC media at a surface or the cell walls of a liquid-crystal display (LC display). The invention therefore also encompasses LC displays having homeotropic alignment of the liquid-crystalline medium (LC medium) without conventional imide alignment layers. The LC media may be supplemented by a polymerisable or polymerised component, which serves for stabilisation of the alignment, for adjustment of the tilt angle and/or as passivation layer.

The present invention relates to liquid-crystalline media (LC media)having negative or positive dielectric anisotropy comprisingself-aligning mesogens (SAMs) which effect homeotropic (vertical)alignment of the LC media at a surface or the cell walls of aliquid-crystal display (LC display). The invention therefore alsoencompasses LC displays having homeotropic alignment of theliquid-crystalline medium (LC medium) without conventional imidealignment layers. The LC media may be supplemented by a polymerisable orpolymerised component, which serves for stabilisation of the alignment,for adjustment of the tilt angle and/or as passivation layer.

The principle of electrically controlled birefringence, the ECB effector also DAP (deformation of aligned phases) effect, was described forthe first time in 1971 (M. F. Schieckel and K. Fahrenschon, “Deformationof nematic liquid crystals with vertical orientation in electricalfields”, Appl. Phys. Lett. 19 (1971), 3912). This was followed by papersby J. F. Kahn (Appl. Phys. Lett. 20 (1972), 1193) and G. Labrunie and J.Robert (J. Appl. Phys. 44 (1973), 4869).

The papers by J. Robert and F. Clerc (SID 80 Digest Techn. Papers(1980), 30), J. Duchene (Displays 7 (1986), 3) and H. Schad (SID 82Digest Techn. Papers (1982), 244) showed that liquid-crystalline phasesmust have high values for the ratio of the elastic constants K₃/K₁, highvalues for the optical anisotropy Δn and values for the dielectricanisotropy of Δ∈≦−0.5 in order to be suitable for use inhigh-information display elements based on the ECB effect.Electro-optical display elements based on the ECB effect havehomeotropic edge alignment (VA technology=vertically aligned).

Displays which use the ECB effect, as so-called VAN (vertically alignednematic) displays, for example in the MVA (multi-domain verticalalignment, for example: Yoshide, H. et al., paper 3.1: “MVA LCD forNotebook or Mobile PCs . . . ”, SID 2004 International Symposium, Digestof Technical Papers, XXXV, Book I, pp. 6 to 9, and Liu, C. T. et al.,paper 15.1: “A 46-inch TFT-LCD HDTV Technology . . . ”, SID 2004International Symposium, Digest of Technical Papers, XXXV, Book II, pp.750 to 753), PVA (patterned vertical alignment, for example: Kim, SangSoo, paper 15.4: “Super PVA Sets New State-of-the-Art for LCD-TV”, SID2004 International Symposium, Digest of Technical Papers, XXXV, Book II,pp. 760 to 763), ASV (advanced super view, for example: Shigeta,Mitzuhiro and Fukuoka, Hirofumi, paper 15.2: “Development of HighQuality LCDTV”, SID 2004 International Symposium, Digest of TechnicalPapers, XXXV, Book II, pp. 754 to 757) modes, have establishedthemselves as one of the three more recent types of liquid-crystaldisplay that are currently the most important, in particular fortelevision applications, besides IPS (in-plane switching) displays (forexample: Yeo, S. D., paper 15.3: “An LC Display for the TV Application”,SID 2004 International Symposium, Digest of Technical Papers, XXXV, BookII, pp. 758 & 759) and the long-known TN (twisted nematic) displays. Thetechnologies are compared in general form, for example, in Souk, Jun,SID Seminar 2004, seminar M-6: “Recent Advances in LCD Technology”,Seminar Lecture Notes, M-6/1 to M-6/26, and Miller, Ian, SID Seminar2004, seminar M-7: “LCD-Television”, Seminar Lecture Notes, M-7/1 toM-7/32. Although the response times of modern ECB displays have alreadybeen significantly improved by addressing methods with overdrive, forexample: Kim, Hyeon Kyeong et al., paper 9.1: “A 57-in. Wide UXGATFT-LCD for HDTV Application”, SID 2004 International Symposium, Digestof Technical Papers, XXXV, Book I, pp. 106 to 109, the achievement ofvideo-compatible response times, in particular on switching of greyshades, is still a problem which has not yet been satisfactorily solved.

Considerable effort is associated with the production of VA displayshaving two or more domains of different preferential direction. It is anaim of this invention to simplify the production processes and thedisplay devices themselves without giving up the advantages of VAtechnology, such as relatively short response times and goodviewing-angle dependence.

VA displays which comprise LC media having positive dielectricanisotropy are described in S. H. Lee et al. Appl. Phys. Lett. (1997),71, 2851-2853. These displays use interdigital electrodes arranged on asubstrate surface (in-plane addressing electrode configuration having acomb-shaped structure), as employed, inter alia, in the commerciallyavailable IPS (in-plane switching) displays (as disclosed, for example,in DE 40 00 451 and EP 0 588 568), and have a homeotropic arrangement ofthe liquid-crystal medium, which changes to a planar arrangement onapplication of an electric field.

Further developments of the above-mentioned display can be found, forexample, in K. S. Hun et al. J. Appl. Phys. (2008), 104, 084515 (DSIPS:‘double-side in-plane switching’ for improvements of driver voltage andtransmission), M. Jiao et al. App. Phys. Lett (2008), 92, 111101 (DFFS:‘dual fringe field switching’ for improved response times) and Y. T. Kimet al. Jap. J. App. Phys. (2009), 48, 110205 (VAS: ‘viewing angleswitchable’ LCD).

In addition, VA-IPS displays are also known under the name positive-VAand HT-VA.

In all such displays (referred to below in general as VA-IPS displays),an alignment layer is applied to both substrate surfaces for homeotropicalignment of the LC medium; the production of this layer has hithertobeen associated with considerable effort.

It is an aim of this invention to simplify the production processesthemselves without giving up the advantages of VA-IPS technology, suchas relatively short response times, good viewing-angle dependence andhigh contrast.

Industrial application of these effects in electro-optical displayelements requires LC phases, which have to satisfy a multiplicity ofrequirements. Particularly important here are chemical resistance tomoisture, air, the materials in the substrate surfaces and physicalinfluences, such as heat, infrared, visible and ultraviolet radiationand direct and alternating electric fields.

Furthermore, industrially usable LC phases are required to have aliquid-crystalline mesophase in a suitable temperature range and lowviscosity.

VA and VA-IPS displays are generally intended to have very high specificresistance at the same time as a large working-temperature range, shortresponse times and a low threshold voltage, with the aid of whichvarious grey shades can be produced.

In conventional VA and VA-IPS displays, a polyimide layer on thesubstrate surfaces ensures homeotropic alignment of the liquid crystal.The production of a suitable alignment layer in the display requiresconsiderable effort. In addition, interactions of the alignment layerwith the LC medium may impair the electrical resistance of the display.Owing to possible interactions of this type, the number of suitableliquid-crystal components is considerably reduced. It would therefore bedesirable to achieve homeotropic alignment of the LC medium withoutpolyimide.

The disadvantage of the active-matrix TN displays frequently used is dueto their comparatively low contrast, the relatively high viewing-angledependence and the difficulty of producing grey shades in thesedisplays.

VA displays have significantly better viewing-angle dependences and aretherefore used principally for televisions and monitors.

A further development are the so-called PS (polymer sustained) or PSA(polymer sustained alignment) displays, for which the term “polymerstabilised” is also occasionally used. The PSA displays aredistinguished by the shortening of the response times withoutsignificant adverse effects on other parameters, such as, in particular,the favourable viewing-angle dependence of the contrast.

In these displays, a small amount (for example 0.3% by weight, typically<1% by weight) of one or more polymerisable compound(s) is added to theLC medium and, after introduction into the LC cell, is polymerised orcrosslinked in situ, usually by UV photopolymerisation, between theelectrodes with or without an applied electrical voltage. The additionof polymerisable mesogenic or liquid-crystalline compounds, also knownas reactive mesogens or “RMs”, to the LC mixture has proven particularlysuitable. PSA technology has hitherto been employed principally for LCmedia having negative dielectric anisotropy.

Unless indicated otherwise, the term “PSA” is used below asrepresentative of PS displays and PSA displays.

In the meantime, the PSA principle is being used in diverse classical LCdisplays. Thus, for example, PSA-VA, PSA-OCB, PSA-IPS, PSA-FFS andPSA-TN displays are known. The polymerisation of the polymerisablecompound(s) preferably takes place with an applied electrical voltage inthe case of PSA-VA and PSA-OCB displays, and with or without an appliedelectrical voltage in the case of PSA-IPS displays. As can bedemonstrated in test cells, the PS(A) method results in a ‘pretilt’ inthe cell. In the case of PSA-OCB displays, for example, it is possiblefor the bend structure to be stabilised so that an offset voltage isunnecessary or can be reduced. In the case of PSA-VA displays, thepretilt has a positive effect on the response times. A standard MVA orPVA pixel and electrode layout can be used for PSA-VA displays. Inaddition, however, it is also possible, for example, to manage with onlyone structured electrode side and no protrusions, which significantlysimplifies production and at the same time results in very good contrastat the same time as very good light transmission.

PSA-VA displays are described, for example, in JP 10-036847 A, EP 1 170626 A2, U.S. Pat. No. 6,861,107, U.S. Pat. No. 7,169,449, US2004/0191428 A1, US 2006/0066793 A1 and US 2006/0103804 A1. PSA-OCBdisplays are described, for example, in T.-J-Chen et al., Jpn. J. Appl.Phys. 45, 2006, 2702-2704 and S. H. Kim, L.-C-Chien, Jpn. J. Appl. Phys.43, 2004, 7643-7647. PSA-IPS displays are described, for example, inU.S. Pat. No. 6,177,972 and Appl. Phys. Lett. 1999, 75(21), 3264. PSA-TNdisplays are described, for example, in Optics Express 2004, 12(7),1221. PSA-VA-IPS displays are disclosed, for example, in WO 2010/089092A1.

Like the conventional LC displays described above, PSA displays can beoperated as active-matrix or passive-matrix displays. In the case ofactive-matrix displays, individual pixels are usually addressed byintegrated, non-linear active elements, such as, for example,transistors (for example thin-film transistors or “TFTs”), while in thecase of passive-matrix displays, individual pixels are usually addressedby the multiplex method, both methods being known from the prior art.

In particular for monitor and especially TV applications, optimisationof the response times, but also of the contrast and luminance (i.e. alsotransmission), of the LC display is still sought after. The PSA methodcan provide crucial advantages here. In particular in the case of PSA-VAdisplays, a shortening of the response times, which correlate with apretilt which can be measured in test cells, can be achieved withoutsignificant adverse effects on other parameters.

In the prior art, polymerisable compounds of the following formula, forexample, are used for PSA-VA:

in which P denotes a polymerisable group, usually an acrylate ormethacrylate group, as described, for example, in U.S. Pat. No.7,169,449.

The effort for the production of a polyimide layer, treatment of thelayer and improvement with bumps or polymer layers is relatively great.A simplifying technology which on the one hand reduces production costsand on the other hand helps to optimise the image quality (viewing-angledependence, contrast, response times) would therefore be desirable.

Spontaneous horizontal to vertical alignment of a liquid-crystal layerwith the aid of nanoparticles based on polyhedral oligomericsilsesquioxanes (simply silsesquioxanes, PSSs below) is reported by thepublication Shie-Chang Jeng et al. Optics Letters (2009), 34, 455-457.From a concentration of about 1% by weight, virtually homeotropicalignment is observed. The pretilt can only be influenced by theconcentration.

The specification US 2008/0198301 A1 likewise proposes PSS as alignmentmaterial. It is evident that the self-alignment functions on ITO and onplanar-aligning polyimide.

The problem of the temperature dependence of the switching operation andthe lack of a passivation layer is not mentioned in eitherspecification. In fact, it has been shown that the degree of homeotropicalignment induced by PSS decreases rapidly with increasing temperature.In addition, a passivation layer is particularly important since thepolyimide layer ensures not only alignment of the LC medium, but alsoelectrical insulation. Without a passivation layer, problems may appearwith the reliability of the display, such as R-DC (‘residual DC’).

A conference poster at SID 2010 (H. Y. Gim et al., P-128) describes thata phenethyl-substituted polyhedral oligomeric silsesquioxane is used ina concentration of 10% by weight in a display without a conventionalalignment layer of the PSA-VA type. The LC medium having negativedielectric anisotropy is homeotropically aligned by the PSS. However,the large amount of dopant has a considerable effect on the propertiesof the LC medium, and the number of liquid-crystal components which canbe employed for an LC display of this type is therefore very limited.

The specification JP 2010170090 A discloses a dendrimer as additive toliquid-crystal mixtures which effects vertical alignment with respect tosubstrates.

Liquid crystals containing amino groups have rarely been describedhitherto since they have virtually never produced desirable properties.The homeotropic alignment of a liquid-crystalline phase comprisingN-alkylated p-(4-alkylcyclohexyl)aniline is reported by J. H. MacMillanet al. Mol. Cryst. Liq. Cryst., 1979, 55, 61-70. Predominantlyhomeotropic alignment of the liquid-crystal matrix on abis-p-aminobenzoic acid ester of hydroquinone is likewise observed (D.C. Schroeder et al. J. Am. Chem. Soc., 1974, 96(13), 4347-4348). Liquidcrystals containing amino groups have hitherto not been employed in LCdisplays.

The existing approaches for achieving display applications without apolyimide layer are therefore still not entirely satisfactory.

The present invention relates firstly to an LC medium comprising alow-molecular-weight liquid-crystalline component and one or moreorganic compounds which contain at least one polar anchor group and atleast one ring group (self-alignment additives). The liquid-crystallinecomponent or the LC medium can have either positive or negativedielectric anisotropy. The LC medium according to the invention ispreferably nematic.

In addition, the LC medium preferably comprises a polymerised orpolymerisable component, where the polymerised component is obtainableby polymerisation of a polymerisable component.

This component enables the LC medium and in particular its alignment tobe stabilised and a desired pretilt optionally to be established.

The present invention furthermore relates to a process for thepreparation of an LC medium in which a low-molecular-weightliquid-crystalline component is mixed with one or more organic compoundswhich contain at least one polar anchor group and at least one ringgroup, and one or more polymerisable compounds and/or assistants areoptionally added. The liquid-crystalline component or the LC medium canhave either positive or negative dielectric anisotropy.

The present invention furthermore relates to a liquid-crystal display(LC display) comprising a liquid-crystal cell (LC cell) having twosubstrates and at least two electrodes, where at least one substrate istransparent to light and at least one substrate has one or twoelectrodes, and a layer of a liquid-crystal medium (LC medium), locatedbetween the substrates, comprising a low-molecular-weightliquid-crystalline component and one or more organic compounds, wherethe organic compound is contains at least one polar anchor group and atleast one ring group and is suitable for effecting homeotropic(vertical) alignment of the LC medium with respect to the substratesurfaces.

In addition, the LC medium of the LC display preferably comprises apolymerised or polymerisable component, where the polymerised componentis obtainable by polymerisation of one or more polymerisable compoundsin the LC medium between the substrates of the LC cell, optionally withapplication of an electrical voltage to the electrodes of the cell orunder the action of another electric field.

The invention furthermore relates to a process for the production of anLC display, preferably of the PSA-VA type, comprising an LC cell havingtwo substrates and at least two electrodes, where at least one substrateis transparent to light and at least one substrate has one or twoelectrodes, comprising the process steps of:

-   -   filling of the cell with an LC medium as described above and        below or in the claims, comprising an organic compound which is        suitable for effecting homeotropic (vertical) alignment of the        LC medium with respect to the substrate surfaces, and optionally    -   polymerisation of a polymerisable component optionally present,        optionally with application of a voltage to the electrodes of        the cell or under the action of an electric field.

The organic compound which contains at least one polar anchor group andat least one ring group (the self-alignment additive) is dissolved ordispersed in the liquid crystal. It effects homeotropic alignment of theliquid crystal with respect to the substrate surfaces (such as, forexample, a glass surface or an ITO- or polyimide-coated surface).Considering the investigations for this invention, it appears that thepolar anchor group interacts with the substrate surface. The organiccompounds on the substrate surface consequently align and inducehomeotropic alignment of the liquid crystal. According to this opinion,the anchor group should be sterically accessible, i.e. should not, forexample, consist of a screened OH group as in 2,6-di-tert-butylphenol.

The self-alignment additive is preferably employed in a concentration ofless than 10% by weight, particularly preferably 8% by weight and veryparticularly 5% by weight. It is preferably employed in a concentrationof at least 0.1% by weight, preferably at least 0.2% by weight. The useof 0.1 to 2.5% by weight of the self-alignment additive generallyalready results in completely homeotropic alignment of the LC layer atconventional cell thicknesses (3 to 4 μm).

The polar anchor group preferably contains no polymerisable group, suchas, for example, acrylate groups.

The polar anchor group of the self-alignment additive preferablyconsists of a group which undergoes a non-covalent interaction with theglass or metal-oxide substrate surface. Suitable groups are polar groupscontaining polar structural elements with atoms selected from N, O, Sand P. The groups should at the same time be sufficiently stable for useas LC medium. In addition, they should have only little effect on theVHR values (‘voltage holding ratio’) of the LC medium. The anchor grouppreferably contains one or more, preferably two or more, of theseheteroatoms.

The polar anchor group preferably consists of one to two structuralelements containing heteroatoms selected from N and O and covalent,linking structures between the heteroatoms and between one or more ofthe heteroatoms and the remainder of the molecule of the formula I(without the anchor group). The polar anchor group preferably containsat least one OH structure or an N atom in a primary, secondary ortertiary amino group.

The term ring group encompasses all ring systems that can be prepared,i.e. also all aromatic, heteroaromatic, alicyclic or heterocyclic ringsystems, also polycyclic ring systems, where at least one part-ringshould preferably contain at least 4 ring atoms. The ring systemproduces a steric effect, i.e. serves as space-filling group, and makesthe compound more or less mesogenic, improving the solubility andcompatibility in the LC medium. The type of the ring group can thereforevary greatly.

The self-alignment additive is preferably an organic compound having arelative molar mass of greater than 100 g/mol, in order that thesubstances are less volatile. It particularly preferably has a relativemolar mass of greater than 126 g/mol in order to achieve an even morestable self-alignment effect. As upper limit, it preferably has arelative molar mass of less than 700 g/mol.

The self-alignment additive preferably has a structure of the formula:

MES-R²

whereMES denotes a group containing at least one ring system, andR² denotes a polar anchor group.

The radical MES preferably denotes a mesogenic group. Mesogenic radicalsare familiar to the person skilled in the art. Mesogenic in thisconnection means, analogously to C. Tschierske et al. Angew. Chem. 2004,116, 6340-86 or according to M. Baron Pure Appl. Chem. 2001, 73,845-895, that the compound contributes to the formation of the desiredmesophase in suitable concentrations and at suitable temperatures. In apreferred embodiment, the self-alignment additives have a structure ofthe general formula I:

R¹-A¹-(Z²-A²)_(m1)-R²  (I)

In formula I, the radical R² denotes a polar anchor group as definedabove and below, and the radical “R¹-A¹-(Z²-A²)_(m1)-” denotes anembodiment of a mesogenic group MES. In particular, in formula (I):

-   A¹ and A² each, independently of one another, denote an aromatic,    heteroaromatic, alicyclic or heterocyclic group, preferably having 4    to 25 C atoms, which may also contain fused rings, and which may    also be mono- or polysubstituted by L, particularly preferably each,    independently of one another, denote 1,4-phenylene,    naphthalene-1,4-diyl or naphthalene-2,6-diyl, where, in addition,    one or more CH groups in these groups may be replaced by N,    cyclohexane-1,4-diyl, in which, in addition, one or more    non-adjacent CH₂ groups may be replaced by O and/or S,    3,3′-bicyclobutylidene, 1,4-cyclohexenylene,    bicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]-octane-1,4-diyl,    spiro[3.3]heptane-2,6-diyl, piperidine-1,4-diyl,    decahydronaphthalene-2,6-diyl,    1,2,3,4-tetrahydronaphthalene-2,6-diyl, indane-2,5-diyl or    octahydro-4,7-methanoindane-2,5-diyl,    perhydrocyclopenta[a]phenanthrene-3,17-diyl (in particular    gonane-3,17-diyl),    -   where all these groups may be unsubstituted or mono- or        polysubstituted by a group L,-   L in each case, independently of one another, denotes OH,    —(CH₂)_(n1)—OH, F, Cl, Br, I, —CN, —NO₂, —NCO, —NCS, —OCN, —SCN,    —C(═O)N(R⁰)₂, —C(═O)R⁰, —N(R⁰)₂, —(CH₂)_(n1)—N(R⁰)₂, optionally    substituted silyl, optionally substituted aryl or cycloalkyl having    6 to 20 C atoms, or straight-chain or branched alkyl, alkoxy,    alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy    having 1 to 25 C atoms, in which, in addition, one or more H atoms    may be replaced by F or Cl,-   Z² in each case, independently of one another, denotes a single    bond, —O—, —S—, —CO—, —CO—O—, —OCO—, —O—CO—O—, —OCH₂—, —CH₂O—,    —SCH₂—, —CH₂S—, —CF₂O—, —OCF₂—, —CF₂S—, —SCF₂—, —(CH₂)_(n1)—,    —CF₂CH₂—, —CH₂CF₂—, —(CF₂)_(n1)—, —CH═CH—, —CF═CF—, —C≡C—,    —CH═CH—COO—, —OCO—CH═CH— or CR⁰R⁰⁰, preferably a single bond,-   R⁰ and R⁰⁰ each, independently of one another, denote H or alkyl    having 1 to 12 C atoms,-   R¹, R², independently of one another, denote H, halogen,    straight-chain, branched or cyclic alkyl having 1 to 25 C atoms, in    which, in addition, one or more non-adjacent CH₂ groups may be    replaced by —NR⁰—, —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— in such    a way that N, O and/or S atoms are not linked directly to one    another, and in which, in addition, one or more tertiary carbon    atoms (CH groups) may be replaced by N, and in which, in addition,    one or more H atoms may be replaced by F or Cl,    -   with the proviso that at least the radical R² contains one or        more heteroatoms selected from N, S and/or O, preferably that at        least the radical R² contains one or more groups NH, OH or SH,-   m1 denotes 0, 1, 2, 3, 4 or 5, and-   n1 denotes 1, 2, 3 or 4.

R² thus encompasses, for example, alcohols, primary, secondary andtertiary amines, ketones, carboxylic acids, thiols, esters and(thio)ethers, and combinations thereof. The structure here may belinear, branched, cyclic or a combination thereof. For example,replacement of a CH₂ group in a radical —CH₃ by —O— produces an OHgroup.

The group R² in the above formulae preferably contains a polar anchorgroup, in particular a group of the formula (A1)

-Sp-[X²—Z³-]_(k)X¹  (A1)

in which

-   -   Sp denotes a single bond or a spacer group defined like Sp^(a)        as defined below for formula M, preferably a spacer group        Sp″-X″, as defined for formula M below, which is connected to        the radical “MES” via the group X″, where Sp″ very particularly        denotes a single bond or an alkylene having 1 to 12 C atoms,    -   X¹ denotes a group —NH₂, —NHR¹¹, —NR₁₁ ², —OR¹¹, —OH, —(CO)OH or        a group of the formula

-   -   R⁰ denotes H or alkyl having 1 to 12 C atoms,    -   X² in each case independently denotes —NH—, —NR¹¹—, —O— or a        single bond,    -   Z³ in each case independently denotes an alkylene group having        1-15 C atoms, carbocyclic rings having 5 or 6 C atoms (for        example optionally substituted benzene, cyclohexane), or        combinations of one or more rings and alkylene groups, in each        of which one or more hydrogen atoms are optionally replaced by        —OH, —OR¹¹, —(CO)OH, —NH₂, —NHR¹¹, —NR¹¹ ₂ or halogen        (preferably F, Cl),    -   R¹¹ in each case independently denotes a halogenated or        unsubstituted alkyl radical having 1 to 15 C atoms, where, in        addition, one or more CH₂ groups in this radical may each be        replaced, independently of one another, by —C≡C—, —CH═CH—,        —(CO)O—, —O(CO)—, —(CO)— or —O— in such a way that O atoms are        not linked directly to one another, and where two radicals R¹¹        are optionally linked to one another to form a ring, and    -   k denotes 0 to 3.

The group R² in the above formulae particularly preferably contains an(N/O)-heteroatom-containing group of the sub-formula (A2)

in which Sp, X¹ and X² are as defined above for formula A1, and

-   -   R¹² denotes H, F, Cl, CN, —OH, —NH₂, or a halogenated or        unsubstituted alkyl radical having 1 to 15 C atoms, where, in        addition, one or more CH₂ groups in this radical may each be        replaced, independently of one another, by —C≡C—, —CH═CH—,        —(CO)O—, —O(CO)—, —(CO)—, —O—, —NH— or —NR¹— in such a way that        0 and N atoms are not linked directly to one another, and    -   n denotes 1, 2 or 3.

The group R² particularly preferably denotes precisely one group of theformula (A1) or (A2).

Particularly preferred nitrogen-containing groups R² are selected from—NH₂, —NH—(CH₂)_(n3)H, —(CH₂)_(n)—NH₂, —(CH₂)_(n)—NH—(CH₂)_(n3)H,—NH—(CH₂)_(n)—NH₂, —NH—(CH₂)_(n)—NH—(CH₂)_(n3)H,—(CH₂)_(n1)—NH—(CH₂)_(n2)—NH₂, —(CH₂)_(n1)—NH—(CH₂)_(n2)—NH—(CH₂)_(n3)H,—O—(CH₂)_(n)—NH₂, —(CH₂)_(n1)—O—(CH₂)_(n)—NH₂,—(CH₂)_(n1)—NH—(CH₂)_(n2)—OH, —O—(CH₂)_(n1)—NH—(CH₂)_(n2)—NH₂,—O—(CH₂)_(n1)—NH—(CH₂)_(n2)—OH,—(CH₂)_(n1)—NH—(CH₂)_(n2)—NH—(CH₂)_(n3)H,

in which n, n1, n2 and n3 denote, independently, 1, 2, 3, 4, 5, 6, 7, 8,9, 10, 11 or 12, in particular 1, 2, 3 or 4.

Particularly preferred nitrogen-free groups R² are selected from —OH,—(CH₂)_(n)—OH, —O—(CH₂)_(n)—OH, —[O—(CH₂)_(n1)]_(n2)—OH, —(CO)OH,—(CH₂)_(n)—(CO)OH, —O—(CH₂)_(n)—(CO)OH or —[O—(CH₂)_(n1)-]_(n2)-(CO)OH,

in which n, n1 and n2 denote, independently, 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11 or 12, in particular 1, 2, 3 or 4.

The term “aryl” denotes an aromatic carbon group or a group derivedtherefrom. The term “heteroaryl” denotes “aryl” as defined abovecontaining one or more heteroatoms.

Aryl and heteroaryl groups may be monocyclic or polycyclic, i.e. theymay contain one ring (such as, for example, phenyl) or two or morerings, which may also be fused (such as, for example, naphthyl) orcovalently bonded (such as, for example, biphenyl), or contain acombination of fused and bonded rings. Heteroaryl groups contain one ormore heteroatoms, preferably selected from O, N, S and Se.

Particular preference is given to mono-, bi- or tricyclic aryl groupshaving 6 to 25 C atoms and mono-, bi- or tricyclic heteroaryl groupshaving 2 to 25 C atoms, which optionally contain fused rings and areoptionally substituted. Preference is furthermore given to 5-, 6- or7-membered aryl and heteroaryl groups, in which, in addition, one ormore CH groups may be replaced by N, S or O in such a way that O atomsand/or S atoms are not linked directly to one another.

Preferred aryl groups are, for example, phenyl, biphenyl, terphenyl,[1,1′:3′,1″]terphenyl-2′-yl, naphthyl, anthracene, binaphthyl,phenanthrene, pyrene, dihydropyrene, chrysene, perylene, tetracene,pentacene, benzopyrene, fluorene, indene, indenofluorene,spirobifluorene, etc.

Preferred heteroaryl groups are, for example, 5-membered rings, such aspyrrole, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, tetrazole,furan, thiophene, selenophene, oxazole, isoxazole, 1,2-thiazole,1,3-thiazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole,1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole,1,2,5-thiadiazole, 1,3,4-thiadiazole, 6-membered rings, such aspyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine,1,2,4-triazine, 1,2,3-triazine, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine,1,2,3,5-tetrazine, or condensed groups, such as indole, isoindole,indolizine, indazole, benzimidazole, benzotriazole, purine,naphthimidazole, phenanthrimidazole, pyridimidazole, pyrazinimidazole,quinoxalinimidazole, benzoxazole, naphthoxazole, anthroxazole,phenanthroxazole, isoxazole, benzothiazole, benzofuran, isobenzofuran,dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5,6-quinoline,benzo-6,7-quinoline, benzo-7,8-quinoline, benzoisoquinoline, acridine,phenothiazine, phenoxazine, benzopyridazine, benzopyrimidine,quinoxaline, phenazine, naphthyridine, azacarbazole, benzocarboline,phenanthridine, phenanthroline, thieno[2,3b]thiophene,thieno[3,2b]thiophene, dithienothiophene, isobenzothiophene,dibenzothiophene, benzothiadiazothiophene, or combinations of thesegroups. The heteroaryl groups may also be substituted by alkyl, alkoxy,thioalkyl, fluorine, fluoroalkyl or further aryl or heteroaryl groups.

The (non-aromatic) alicyclic and heterocyclic groups encompass bothsaturated rings, i.e. those containing exclusively single bonds, andalso partially unsaturated rings, i.e. those which may also containmultiple bonds. Heterocyclic rings contain one or more heteroatoms,preferably selected from Si, O, N, S and Se.

The (non-aromatic) alicyclic and heterocyclic groups may be monocyclic,i.e. contain only one ring (such as, for example, cyclohexane), orpolycyclic, i.e. contain a plurality of rings (such as, for example,decahydronaphthalene or bicyclooctane). Particular preference is givento saturated groups. Preference is furthermore given to mono-, bi- ortricyclic groups having 3 to 25 C atoms, which optionally contain fusedrings and are optionally substituted. Preference is furthermore given to5-, 6-, 7- or 8-membered carbocyclic groups, in which, in addition, oneor more C atoms may be replaced by Si and/or one or more CH groups maybe replaced by N and/or one or more non-adjacent CH₂ groups may bereplaced by —O— and/or —S—.

Preferred alicyclic and heterocyclic groups are, for example, 5-memberedgroups, such as cyclopentane, tetrahydrofuran, tetrahydrothiofuran,pyrrolidine, 6-membered groups, such as cyclohexane, cyclohexene,tetrahydropyran, tetrahydrothiopyran, 1,3-dioxane, 1,3-dithiane,piperidine, 7-membered groups, such as cycloheptane, and fused groups,such as tetrahydronaphthalene, decahydronaphthalene, indane,bicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl,spiro[3.3]heptane-2,6-diyl, octahydro-4,7-methanoindane-2,5-diyl.

In connection with the present invention, the term “alkyl” denotes astraight-chain or branched, saturated or unsaturated, preferablysaturated, aliphatic hydrocarbon radical having 1 to 15 (i.e. 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15) carbon atoms.

The term “cyclic alkyl” encompasses alkyl groups which have at least onecarbocyclic part, i.e., for example, also cycloalkylalkyl,alkylcycloalkyl and alkylcycloalkylalkyl. The carbocyclic groupsencompass, for example, cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, cycloheptyl, cyclooctyl, etc.

“Halogen” in connection with the present invention stands for fluorine,chlorine, bromine or iodine, preferably for fluorine or chlorine.

Particularly preferred compounds of the formula I are selected from thefollowing illustrative compounds, which at the same time representparticularly preferred groups MES and R² of the self-alignmentadditives:

In a further preferred embodiment of the invention, use is made oforganic compounds containing the polar anchor group or compounds of theformula I which, besides the polar anchor, contain one or morepolymerisable groups as further functionalisation (compare group P^(a)or P^(b) below). Preferred polymerisable groups are groups such asacrylate, methacrylate, fluoroacrylate, oxetane, vinyloxy or epoxidegroups, particularly preferably acrylate and methacrylate. The inclusionof compounds of the formula I in the polymerisation permanentlyimmobilises the compounds, causing them to retain their function.

An advantage of the LC displays according to the invention is that thedisplay achieves the desired homeotropic alignment without theconventional polyimide alignment layer. This alignment is generally alsoretained at elevated temperature. Due to the polymer stabilisation, thehomeotropic alignment is additionally stabilised; improved temperaturestability of the electro-optical switching is thus achieved. Thepolymer-stabilised displays according to the invention are distinguishedby improved response times and a better contrast ratio (pretilt angleand temperature dependence of the contrast). The polymerised componentoptionally present can at the same time serve as a passivation layer,which increases the reliability of the display.

The organic compounds containing the polar anchor group or the compoundsof the formula I do not destabilise the nematic phase of the LC mediumthanks to their structure, but instead contribute to the stability. Inaddition, the relatively small amount of compounds of the formula I hasvirtually no effect on the properties of the LC media. It is thereforepossible to use a broad range of liquid-crystal components in the LCdisplay.

The LC displays according to the invention therefore preferably have noalignment layer for homeotropic alignment on the surfaces of the LCcell, i.e. they are polyimide-free. In the case where the LC displaysnevertheless have alignment layers on one or both sides, thesepreferably consist of polyimide. The alignment layers are preferably notrubbed. The rubbing of the alignment layer, a particularlytime-consuming step in production, which was hitherto necessary is thussuperfluous. The unrubbed polyimide layer can serve as passivationlayer.

In a particular embodiment, the LC displays according to the inventionuse an LC medium having negative dielectric anisotropy (Δ∈≦−1.5). Ingeneral, the display is a VA display having electrodes arranged onopposite sides of the LC cell, preferably having electrodes which arearranged in such a way that they are able to generate an electric fieldaligned predominantly perpendicular to the substrate surface. Typicalsubstrates used are those which are used from the VAN mode and PSA-VA(structuring of the electrodes is therefore possible).

In a particular embodiment, the LC displays according to the inventionuse an LC medium having positive dielectric anisotropy (Δ∈≦1.5). Ingeneral, the display is a VA-IPS display having electrodes arranged onone side of the LC cell, preferably having electrodes which are arrangedin such a way that they are able to generate an electric field alignedpredominantly planar to the substrate surface, for example interdigitalelectrodes (in-plane addressing electrode configuration having acomb-shaped structure).

The LC displays are provided in a conventional manner with polariser(s),which make(s) the LC medium switching operation visible.

The polymerised component of the LC cell (polymer) is obtainable bypolymerisation of a polymerisable component (monomer). In general, themonomers are firstly dissolved in the LC medium and are polymerised inthe LC cell after homeotropic alignment or a high tilt angle of the LCmedium has been established. In order to support the desired alignment,a voltage can be applied to the LC cell. In the simplest case, such avoltage is superfluous, and the desired alignment becomes establishedmerely through the nature of the LC medium and the cell geometry.

Suitable monomers (polymerisable component) for the LC medium are thosefrom the prior art which are used for PSA-VA displays, in particularpolymerisable compounds of the formula M mentioned below and/or of theformulae M1 to M29. The LC media according to the invention for use inPSA displays preferably comprise <5% by weight, particularly preferably<1% by weight and very particularly preferably <0.5% by weight, ofpolymerisable compounds, in particular polymerisable compounds of theformulae mentioned below. In order to achieve an adequate effect, 0.2%by weight or more is preferably employed. The optimum amount isdependent on the layer thickness.

Suitable monomers of the polymerisable component of the LC medium aredescribed by the following formula M:

P^(a)-(Sp^(a))_(s1)-A²-(Z¹-A¹)_(n)-(Sp^(b))_(s2)-P^(b)  M

in which the individual radicals have the following meanings:

-   P^(a), P^(b) each, independently of one another, denote a    polymerisable group,-   Sp^(a), Sp^(b) on each occurrence, identically or differently,    denote a spacer group,-   s1, s2 each, independently of one another, denote 0 or 1,-   A¹, A² each, independently of one another, denote a radical selected    from the following groups:    -   a) the group consisting of trans-1,4-cyclohexylene,        1,4-cyclohexenylene and 4,4″-bicyclohexylene, in which, in        addition, one or more non-adjacent CH₂ groups may be replaced by        —O— and/or —S— and in which, in addition, one or more H atoms        may be replaced by F,    -   b) the group consisting of 1,4-phenylene and 1,3-phenylene, in        which, in addition, one or two CH groups may be replaced by N        and in which, in addition, one or more H atoms may be replaced        by L,    -   c) the group consisting of tetrahydropyran-2,5-diyl,        1,3-dioxane-2,5-diyl, tetrahydrofuran-2,5-diyl,        cyclobutane-1,3-diyl, piperidine-1,4-diyl, thiophene-2,5-diyl        and selenophene-2,5-diyl, each of which may also be mono- or        polysubstituted by L,    -   d) the group consisting of saturated, partially unsaturated or        fully unsaturated, and optionally substituted, polycyclic        radicals having 5 to 20 cyclic C atoms, one or more of which        may, in addition, be replaced by heteroatoms, preferably        selected from the group consisting of        bicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl,        spiro[3.3]heptane-2,6-diyl,

-   -   -   where, in addition, one or more H atoms in these radicals            may be replaced by L, and/or one or more double bonds may be            replaced by single bonds, and/or one or more CH groups may            be replaced by N,

-   n denotes 0, 1, 2 or 3,

-   Z¹ in each case, independently of one another, denotes —CO—O—,    —O—CO—, —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂—, or —(CH₂)_(n)—, where n is    2, 3 or 4, —O—, —CO—, —C(R^(c)R^(d))—, —CH₂CF₂—, —CF₂CF₂— or a    single bond,

-   L on each occurrence, identically or differently, denotes F, Cl, CN,    SCN, SF₅ or straight-chain or branched, in each case optionally    fluorinated, alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl,    alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms,

-   R⁰, R⁰⁰ each, independently of one another, denote H, F or    straight-chain or branched alkyl having 1 to 12 C atoms, in which,    in addition, one or more H atoms may be replaced by F,

-   M denotes —O—, —S—, —CH₂—, —CHY¹— or —CY¹Y²—, and

-   Y¹ and Y² each, independently of one another, have one of the    meanings indicated above for R⁰ or denote Cl or CN, and preferably    H, F, Cl, CN, OCF₃ or CF₃,

-   W¹, W² each, independently of one another, denote —CH₂CH₂—, —CH═CH—,    —CH₂—O—, —O—CH₂—, —C(R^(c)R^(d))— or —O—,

-   R^(c) and R^(d) each, independently of one another, denote H or    alkyl having 1 to 6 C atoms, preferably H, methyl or ethyl.

The polymerisable group P^(a,b) is a group which is suitable for apolymerisation reaction, such as, for example, free-radical or ionicchain polymerisation, polyaddition or polycondensation, or for apolymer-analogous reaction, for example addition or condensation onto amain polymer chain. Particular preference is given to groups for chainpolymerisation, in particular those containing a C═C double bond or—C≡C— triple bond, and groups which are suitable for polymerisation withring opening, such as, for example, oxetane or epoxide groups.

Preferred groups P^(a,b) are selected from the group consisting ofCH₂═CW¹—CO—O—, CH₂═CW¹—CO—,

CH₂═CW²—(O)_(k3)—, CW¹═CH—CO—(O)_(k3)—, CW¹═CH—CO—NH—, CH₂═CW¹—CO—NH—,CH₃—CH═CH—O—, (CH₂═CH)₂CH—OCO—, (CH₂═CH—CH₂)₂CH—OCO—, (CH₂═CH)₂CH—O—,(CH₂═CH—CH₂)₂N—, (CH₂═CH—CH₂)₂N—CO—, HO—CW²W³—, HS—CW²W³—, HW²N—,HO—CW²W³—NH—, CH₂═CW¹—CO—NH—, CH₂═CH—(COO)_(k1)-Phe-(O)_(k2)—,CH₂═CH—(CO)_(k1)-Phe-(O)_(k2)—, Phe-CH═CH—, HOOC—, OCN— and W⁴W⁵W⁶Si—,in which W¹ denotes H, F, Cl, CN, CF₃, phenyl or alkyl having 1 to 5 Catoms, in particular H, F, Cl or CH₃, W² and W³ each, independently ofone another, denote H or alkyl having 1 to 5 C atoms, in particular H,methyl, ethyl or n-propyl, W⁴, W⁵ and W⁶ each, independently of oneanother, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms,W⁷ and W⁸ each, independently of one another, denote H, Cl or alkylhaving 1 to 5 C atoms, Phe denotes 1,4-phenylene, which is optionallysubstituted by one or more radicals L as defined above which are otherthan P-Sp-, k₁, k₂ and k₃ each, independently of one another, denote 0or 1, k₃ preferably denotes 1, and k₄ denotes an integer from 1 to 10.

Particularly preferred groups P^(a,b) are selected from the groupconsisting of CH₂═CW¹—CO—O—, CH₂═CW¹—CO—,

CH₂═CW²—O—, CW¹═CH—CO—(O)_(k3)—, CW¹═CH—CO—NH—, CH₂═CW¹—CO—NH—,(CH₂═CH)₂CH—OCO—, (CH₂═CH—CH₂)₂CH—OCO—, (CH₂═CH)₂CH—O—, (CH₂═CH—CH₂)₂N—,(CH₂═CH—CH₂)₂N—CO—, CH₂═CW¹—CO—NH—, CH₂═CH—(COO)_(k1)-Phe-(O)_(k2)—,CH₂═CH—(CO)_(k1)-Phe-(O)_(k2)—, Phe-CH═CH— and W⁴W⁵W⁶Si—, in which W¹denotes H, F, Cl, CN, CF₃, phenyl or alkyl having 1 to 5 C atoms, inparticular H, F, Cl or CH₃, W² and W³ each, independently of oneanother, denote H or alkyl having 1 to 5 C atoms, in particular H,methyl, ethyl or n-propyl, W⁴, W⁵ and W⁶ each, independently of oneanother, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms,W⁷ and W⁸ each, independently of one another, denote H, Cl or alkylhaving 1 to 5 C atoms, Phe denotes 1,4-phenylene, k₁, k₂ and k₃ each,independently of one another, denote 0 or 1, k₃ preferably denotes 1,and k₄ denotes an integer from 1 to 10.

Very particularly preferred groups P^(a,b) are selected from the groupconsisting of CH₂═CW¹—CO—O—, in particular CH₂═CH—CO—O—,CH₂═C(CH₃)—CO—O— and CH₂═CF—CO—O—, furthermore CH₂═CH—O—,(CH₂═CH)₂CH—O—CO—, (CH₂═CH)₂CH—O—,

Very particularly preferred groups P^(a,b) are therefore selected fromthe group consisting of acrylate, methacrylate, fluoroacrylate,furthermore vinyloxy, chloroacrylate, oxetane and epoxide groups, and ofthese preferably an acrylate or methacrylate group.

Preferred spacer groups Sp^(a,b) are selected from the formula Sp″-X″,so that the radical P^(a/b)-Sp^(a/b)- conforms to the formulaP^(a/b)-Sp″-X″—, where

-   Sp″ denotes alkylene having 1 to 20, preferably 1 to 12, C atoms,    which is optionally mono- or polysubstituted by F, Cl, Br, I or CN    and in which, in addition, one or more non-adjacent CH₂ groups may    each be replaced, independently of one another, by —O—, —S—, —NH—,    —N(R⁰)—, —Si(R⁰⁰R⁰⁰⁰)—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —S—CO—,    —CO—S—, —N(R⁰⁰)—CO—O—, —O—CO—N(R⁰⁰)—, —N(R⁰⁰)—CO—N(R⁰⁰)—, —CH═CH— or    —C≡C— in such a way that O and/or S atoms are not linked directly to    one another,-   X″ denotes —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CO—N(R⁰⁰)—,    —N(R⁰⁰)—CO—, —N(R⁰⁰—CO—N(R⁰⁰)—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—,    —CF₂O—, —OCF₂—, —CF₂S—, —SCF₂—, —CF₂CH₂—, —CH₂CF₂—, —CF₂CF₂—,    —CH═N—, —N═CH—, —N═N—, —CH═CR⁰—, —CY²═CY³—, —C≡C—, —CH═CH—CO—O—,    —O—CO—CH═CH— or a single bond,-   R⁰⁰ and R⁰⁰⁰ each, independently of one another, denote H or alkyl    having 1 to 12 C atoms, and-   Y² and Y³ each, independently of one another, denote H, F, Cl or CN.-   X″ is preferably —O—, —S—, —CO—, —COO—, —OCO—, —O—COO—, —CO—NR⁰—,    —NR⁰—CO—, —NR⁰—CO—NR⁰— or a single bond.

Typical spacer groups Sp″ are, for example, —(CH₂)_(p1)—,—(CH₂CH₂O)_(q1)—CH₂CH₂—, —CH₂CH₂—S—CH₂CH₂—, —CH₂CH₂—NH—CH₂CH₂— or—(SiR⁰⁰R⁰⁰⁰—O)_(p1)—, in which p1 is an integer from 1 to 12, q1 is aninteger from 1 to 3, and R⁰⁰ and R⁰⁰⁰ have the meanings indicated above.

Particularly preferred groups -Sp″-X″— are —(CH₂)_(p1)—, —(CH₂)_(p1)—O—,—(CH₂)_(p1)—O—CO—, —(CH₂)_(p1)—O—CO—O—, in which p1 and q1 have themeanings indicated above.

Particularly preferred groups Sp″ are, for example, in each casestraight-chain ethylene, propylene, butylene, pentylene, hexylene,heptylene, octylene, nonylene, decylene, undecylene, dodecylene,octadecylene, ethyleneoxyethylene, methyleneoxybutylene,ethylenethioethylene, ethylene-Nmethyliminoethylene, 1-methylalkylene,ethenylene, propenylene and butenylene.

Particularly preferred monomers are the following:

in which the individual radicals have the following meanings:

-   P¹ and P² each, independently of one another, denote a polymerisable    group as defined for formula I, preferably an acrylate,    methacrylate, fluoroacrylate, oxetane, vinyloxy or epoxide group,-   Sp¹ and Sp² each, independently of one another, denote a single bond    or a spacer group, preferably having one of the meanings indicated    above and below for Sp^(a), and particularly preferably    —(CH₂)_(p1)—, —(CH₂)_(p1)—O—, —(CH₂)_(p1)—CO—O— or    —(CH₂)_(p1)—O—CO—O—, in which p1 is an integer from 1 to 12, and    where the linking to the adjacent ring in the last-mentioned groups    takes place via the O atom,    -   where, in addition, one or more of the radicals P¹-Sp¹- and        P²-Sp²- may denote a radical R^(aa), with the proviso that at        least one of the radicals P¹-Sp¹- and P²-Sp²- present does not        denote R^(aa),-   R^(aa) denotes H, F, Cl, CN or straight-chain or branched alkyl    having 1 to 25 C atoms, in which, in addition, one or more    non-adjacent CH₂ groups may each be replaced, independently of one    another, by C(R⁰)═C(R⁰⁰)—, —C≡C—, —N(R⁰)—, —O—, —S—, —CO—, —CO—O—,    —O—CO—, —O—CO—O— in such a way that O and/or S atoms are not linked    directly to one another, and in which, in addition, one or more H    atoms may be replaced by F, Cl, CN or P¹-Sp¹-, particularly    preferably straight-chain or branched, optionally mono- or    polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl,    alkoxycarbonyl or alkylcarbonyloxy having 1 to 12 C atoms (where the    alkenyl and alkynyl radicals have at least two C atoms and the    branched radicals have at least three C atoms),-   R⁰, R⁰⁰ each, independently of one another, denote H or alkyl having    1 to 12 C atoms,-   R^(y) and R^(z) each, independently of one another, denote H, F, CH₃    or CF₃,-   Z¹ denotes —O—, —CO—, —C(R^(y)R^(z))— or —CF₂CF₂—,-   Z² and Z³ each, independently of one another, denote —CO—O—, —O—CO—,    —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂— or —(CH₂)_(n)—, where n is 2, 3 or 4,-   L on each occurrence, identically or differently, denotes F, Cl, CN,    SCN, SF₅ or straight-chain or branched, optionally mono- or    polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl,    alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12    C atoms, preferably F,-   L′ and L″ each, independently of one another, denote H, F or Cl,-   r denotes 0, 1, 2, 3 or 4,-   s denotes 0, 1, 2 or 3,-   t denotes 0, 1 or 2, and-   x denotes 0 or 1.

The LC medium or the polymerisable component preferably comprises one ormore compounds selected from the group of the formulae M1-M21,particularly preferably from the group of the formulae M2-M15, veryparticularly preferably from the group of the formulae M2, M3, M9, M14and M15.

The LC medium or the polymerisable component preferably comprises nocompounds of the formula M10 in which Z² and Z³ denote —(CO)O— or—O(CO)—.

For the production of PSA displays, the polymerisable compounds arepolymerised or crosslinked (if a polymerisable compound contains two ormore polymerisable groups) by in-situ polymerisation in the LC mediumbetween the substrates of the LC display, optionally with application ofa voltage. The polymerisation can be carried out in one step. It is alsopossible firstly to carry out the polymerisation with application of avoltage in a first step in order to produce a pretilt angle, andsubsequently, in a second polymerisation step, to polymerise orcrosslink the compounds which have not fully reacted in the first stepwithout an applied voltage (“end curing”).

Suitable and preferred polymerisation methods are, for example, thermalor photopolymerisation, preferably photopolymerisation, in particular UVphotopolymerisation. One or more initiators can optionally also be addedhere. Suitable conditions for the polymerisation and suitable types andamounts of initiators are known to the person skilled in the art and aredescribed in the literature. Suitable for free-radical polymerisationare, for example, the commercially available photoinitiatorsIrgacure651®, Irgacure184®, Irgacure907®, Irgacure369® or Darocure1173®(Ciba AG). If an initiator is employed, its proportion is preferably0.001 to 5% by weight, particularly preferably 0.001 to 1% by weight.

The polymerisable compounds according to the invention are also suitablefor polymerisation without an initiator, which is associated withconsiderable advantages, such as, for example, lower material costs and,in particular, reduced contamination of the LC medium by possibleresidual amounts of the initiator or degradation products thereof. Thepolymerisation can thus also be carried out without addition of aninitiator. The LC medium thus, in a preferred embodiment, comprises nopolymerisation initiator.

The polymerisable component or the LC medium may also comprise one ormore stabilisers in order to prevent undesired spontaneouspolymerisation of the RMs, for example during storage or transport.Suitable types and amounts of stabilisers are known to the personskilled in the art and are described in the literature. Particularlysuitable are, for example, the commercially available stabilisers fromthe Irganox® series (Ciba AG), such as, for example, Irganox® 1076. Ifstabilisers are employed, their proportion, based on the total amount ofthe RMs or the polymerisable component, is preferably 10-10,000 ppm,particularly preferably 50-500 ppm.

Besides the SAMs described above and the optional polymerisablecompounds (M) described above, the LC media for use in the LC displaysaccording to the invention comprise an LC mixture (“host mixture”)comprising one or more, preferably two or more, low-molecular-weight(i.e. monomeric or unpolymerised) compounds. The latter are stable orunreactive with respect to a polymerisation reaction under theconditions used for the polymerisation of the polymerisable compounds.In principle, a suitable host mixture is any dielectrically negative orpositive LC mixture which is suitable for use in conventional VA andVA-IPS displays.

Suitable LC mixtures are known to the person skilled in the art and aredescribed in the literature. LC media for VA displays having negativedielectric anisotropy are described in EP 1 378 557 A1.

Suitable LC mixtures having positive dielectric anisotropy which aresuitable for LCDs and especially for IPS displays are known, forexample, from JP 07-181 439 (A), EP 0 667 555, EP 0 673 986, DE 195 09410, DE 195 28 106, DE 195 28 107, WO 96/23 851 and WO 96/28 521.

Preferred embodiments of the liquid-crystalline medium having negativedielectric anisotropy according to the invention are indicated below:

-   a) LC medium which additionally comprises one or more compounds    selected from the group of the compounds of the formulae A, B and C,

-   -   in which    -   R^(2A), R^(2B) and R^(2C) each, independently of one another,        denote H, an alkyl radical having up to 15 C atoms which is        unsubstituted, monosubstituted by CN or CF₃ or at least        monosubstituted by halogen, where, in addition, one or more CH₂        groups in these radicals may be replaced by —O—, —S—,

—C≡C—, —CF₂O—, —OCF₂—, —OC—O— or —O—CO— in such a way that O atoms arenot linked directly to one another,

-   -   L¹⁻⁴ each, independently of one another, denote F, Cl, CF₃ or        CHF₂,    -   Z² and Z^(2′) each, independently of one another, denote a        single bond, —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—,        —COO—, —OCO—, —C₂F₄—, —CF═CF—, —CH═CHCH₂O—,    -   p denotes 1 or 2,    -   q denotes 0 or 1, and    -   v denotes 1 to 6.

In the compounds of the formulae A and B, Z² can have identical ordifferent meanings. In the compounds of the formula B, Z² and Z^(2′) canhave identical or different meanings.

In the compounds of the formulae A, B and C, R^(2A), R^(2B) and R^(2C)each preferably denote alkyl having 1-6 C atoms, in particular CH₃,C₂H₅, n-C₃H₇, n-C₄H₉, n-C₅H₁₁.

In the compounds of the formulae A and B, L¹, L², L³ and L⁴ preferablydenote L¹=L²=F and L³=L⁴=F, furthermore L¹=F and L²=Cl, L¹ ═Cl and L²=F,L³=F and L⁴=Cl, L³═Cl and L⁴=F. Z² and Z^(2′) in the formulae A and Bpreferably each, independently of one another, denote a single bond,furthermore a —C₂H₄— bridge.

If Z²=—C₂H₄— in the formula B, Z^(2′) is preferably a single bond, or ifZ^(2′)=—C₂H₄—, Z² is preferably a single bond. In the compounds of theformulae A and B, (O)C_(v)H_(2v+1) preferably denotes OC_(v)H_(2v+1),furthermore C_(v)H_(2v+1). In the compounds of the formula C,(O)C_(v)H_(2v+1) preferably denotes C_(v)H_(2v+1). In the compounds ofthe formula C, L³ and L⁴ preferably each denote F.

Preferred compounds of the formulae A, B and C are shown below:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms.    -   Particularly preferred mixtures according to the invention        comprise one or more compounds of the formulae A-2, A-8, A-14,        A-29, A-35, B-2, B-11, B-16 and C-1.    -   The proportion of compounds of the formulae A and/or B in the        mixture as a whole is preferably at least 20% by weight.    -   Particularly preferred media according to the invention comprise        at least one compound of the formula C-1,

-   -   in which alkyl and alkyl* have the meanings indicated above,        preferably in amounts of >3% by weight, in particular >5% by        weight and particularly preferably 5-25% by weight.

-   b) LC medium which additionally comprises one or more compounds of    the following formula:

-   -   in which the individual radicals have the following meanings:

-   -   R³ and R⁴ each, independently of one another, denote alkyl        having 1 to 12 C atoms, in which, in addition, one or two        non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,        —O—CO— or —CO—O— in such a way that O atoms are not linked        directly to one another,    -   Z^(y) denotes —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—,        —CO—O—, —O—CO—, —C₂F₄—, —CF═CF—, —CH═CH—CH₂O— or a single bond,        preferably a single bond.    -   The compounds of the formula ZK are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, and        alkenyl and alkenyl* denote a straight-chain alkenyl radical        having 2-6 C atoms. Alkenyl preferably denotes CH₂═CH—,        CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—,        CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

-   c) LC medium which additionally comprises one or more compounds of    the following formula:

-   -   in which the individual radicals on each occurrence, identically        or differently, have the following meanings:    -   R⁵ and R⁶ each, independently of one another, have one of the        meanings indicated above for R^(3/4),

-   -   and    -   e denotes 1 or 2.    -   The compounds of the formula DK are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, and        alkenyl and alkenyl* each, independently of one another, denote        a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and        alkenyl* preferably denote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—,        CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or        CH₃—CH═CH—(CH₂)₂—.

-   d) LC medium which additionally comprises one or more compounds of    the following formula:

-   -   in which the individual radicals have the following meanings:

-   -   f denotes 0 or 1,    -   R¹ and R² each, independently of one another, denote alkyl        having 1 to 12 C atoms, where, in addition, one or two        non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—,        —CF═CF—, —CO—, —O(CO)— or —(CO)O— in such a way that O atoms are        not linked directly to one another,    -   Z^(x) and Z^(y) each, independently of one another, denote        —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —CO—O—,        —O—CO—, —C₂F₄—, —CF═CF—, —CH═CH—CH₂O— or a single bond,        preferably a single bond,    -   L¹ and L² each, independently of one another, denote F, Cl,        OCF₃, CF₃, CH₃, CH₂F, CHF₂.    -   Preferably, both radicals L¹ and L² denote F or one of the        radicals L¹ and L² denotes F and the other denotes Cl.    -   The compounds of the formula LY are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which R¹ has the meaning indicated above, alkyl denotes a        straight-chain alkyl radical having 1-6 C atoms, (O) denotes an        oxygen atom or a single bond, and v denotes an integer from 1        to 6. R¹ preferably denotes straight-chain alkyl having 1 to 6 C        atoms or straight-chain alkenyl having 2 to 6 C atoms, in        particular CH₃, C₂H₅, n-C₃H₇, n-C₄H₉, n-C₅H₁₁, CH₂═CH—,        CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—,        CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

-   e) LC medium which additionally comprises one or more compounds    selected from the group consisting of the following formulae:

-   -   in which alkyl denotes C₁₋₆-alkyl, Lx denotes H or F, and X        denotes F, Cl, OCF₃, OCHF₂ or OCH═CF₂. Particular preference is        given to compounds of the formula G1 in which X denotes F.

-   f) LC medium which additionally comprises one or more compounds    selected from the group consisting of the following formulae:

-   -   in which R⁵ has one of the meanings indicated above for R¹,        alkyl denotes C₁₋₆-alkyl, d denotes 0 or 1, and z and m each,        independently of one another, denote an integer from 1 to 6. R⁵        in these compounds is particularly preferably C₁₋₆-alkyl or        -alkoxy or C₂₋₆-alkenyl, d is preferably 1. The LC medium        according to the invention preferably comprises one or more        compounds of the above-mentioned formulae in amounts of 5% by        weight.

-   g) LC medium which additionally comprises one or more biphenyl    compounds selected from the group consisting of the following    formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, and        alkenyl and alkenyl* each, independently of one another, denote        a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and        alkenyl* preferably denote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—,        CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or        CH₃—CH═CH—(CH₂)₂—.    -   The proportion of the biphenyls of the formulae B1 to B3 in the        LC mixture is preferably at least 3% by weight, in particular        ≧5% by weight.    -   The compounds of the formula B2 are particularly preferred.    -   The compounds of the formulae B1 to B3 are preferably selected        from the group consisting of the following sub-formulae:

-   -   in which alkyl* denotes an alkyl radical having 1-6 C atoms. The        medium according to the invention particularly preferably        comprises one or more compounds of the formulae B1a and/or B2c.

-   h) LC medium which additionally comprises one or more terphenyl    compounds of the following formula:

-   -   in which R⁵ and R⁶ each, independently of one another, have one        of the meanings indicated above for R¹, and

-   -   each, independently of one another, denote

-   -   in which L⁵ denotes F or Cl, preferably F, and L⁶ denotes F, Cl,        OCF₃, CF₃, CH₃, CH₂F or CHF₂, preferably F.    -   The compounds of the formula T are preferably selected from the        group consisting of the following sub-formulae:

-   -   in which R denotes a straight-chain alkyl or alkoxy radical        having 1-7 C atoms, R* denotes a straight-chain alkenyl radical        having 2-7 C atoms, (O) denotes an oxygen atom or a single bond,        and m denotes an integer from 1 to 6. R* preferably denotes        CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—,        CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.    -   R preferably denotes methyl, ethyl, propyl, butyl, pentyl,        hexyl, methoxy, ethoxy, propoxy, butoxy or pentoxy.    -   The LC medium according to the invention preferably comprises        the terphenyls of the formula T and the preferred sub-formulae        thereof in an amount of 0.5-30% by weight, in particular 1-20%        by weight.    -   Particular preference is given to compounds of the formulae T1,        T2, T3 and T21. In these compounds, R preferably denotes alkyl,        furthermore alkoxy, each having 1-5 C atoms.    -   The terphenyls are preferably employed in mixtures according to        the invention if the Δn value of the mixture is to be 0.1.        Preferred mixtures comprise 2-20% by weight of one or more        terphenyl compounds of the formula T, preferably selected from        the group of compounds T1 to T22.

-   i) LC medium which additionally comprises one or more compounds    selected from the group consisting of the following formulae:

-   -   in which R¹ and R² have the meanings indicated above for formula        LY and preferably each, independently of one another, denote        straight-chain alkyl having 1 to 6 C atoms or straight-chain        alkenyl having 2 to 6 C atoms.    -   Preferred media comprise one or more compounds selected from the        formulae 01, 03 and 04.

-   k) LC medium which additionally comprises one or more compounds of    the following formula:

-   -   in which

-   -   R⁹ denotes H, CH₃, C₂H₅ or n-C₃H₇, (F) denotes an optional        fluorine substituent, and q denotes 1, 2 or 3, and R⁷ has one of        the meanings indicated for R¹, preferably in amounts of >3% by        weight, in particular ≧5% by weight and very particularly        preferably 5-30% by weight.    -   Particularly preferred compounds of the formula FI are selected        from the group consisting of the following sub-formulae:

-   -   in which R⁷ preferably denotes straight-chain alkyl, and R⁹        denotes CH₃, C₂H₅ or n-C₃H₇. Particular preference is given to        the compounds of the formulae FI1, FI2 and FI3.

-   m) LC medium which additionally comprises one or more compounds    selected from the group consisting of the following formulae:

-   -   in which R⁸ has the meaning indicated for R¹ for formula LY, and        alkyl denotes a straight-chain alkyl radical having 1-6 C atoms.

-   n) LC medium which additionally comprises one or more compounds    which contain a tetrahydronaphthyl or naphthyl unit, such as, for    example, the compounds selected from the group consisting of the    following formulae:

-   -   in which R¹⁰ and R¹¹ each, independently of one another, have        one of the meanings indicated for R¹ for formula LY, preferably        denote straight-chain alkyl or alkoxy having 1 to 6 C atoms or        straight-chain alkenyl having 2 to 6 C atoms, and Z¹ and Z²        each, independently of one another, denote —C₂H₄—, —CH═CH—,        —(CH₂)₄—, —(CH₂)₃O—, —O(CH₂)₃—, —CH═CH—CH₂CH₂—, —CH₂CH₂CH═CH—,        —CH₂O—, —OCH₂—, —CO—O—, —O—CO—, —C₂F₄—, —CF═CF—, —CF═CH—,        —CH═CF—, —CH₂— or a single bond.

-   o) LC medium which additionally comprises one or more    difluorodibenzochromans and/or chromans of the following formulae:

-   -   in which R¹⁰ and R¹¹ each, independently of one another, have        the meaning indicated above for R¹ in formula LY, and c denotes        0 or 1, preferably in amounts of 3 to 20% by weight, in        particular in amounts of 3 to 15% by weight.    -   Particularly preferred compounds of the formulae BC and CR are        selected from the group consisting of the following        sub-formulae:

-   -   in which alkyl and alkyl* each, independently of one another,        denote a straight-chain alkyl radical having 1-6 C atoms, and        alkenyl and alkenyl* each, independently of one another, denote        a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and        alkenyl* preferably denote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—,        CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or        CH₃—CH═CH—(CH₂)₂—.    -   Very particular preference is given to mixtures comprising one,        two or three compounds of the formula BC2.

-   p) LC medium which additionally comprises one or more fluorinated    phenanthrenes and/or dibenzofurans of the following formulae:

-   -   in which R¹¹ and R¹² each, independently of one another, have        the meaning indicated above for R¹ in formula LY, b denotes 0 or        1, L denotes F, and r denotes 1, 2 or 3.    -   Particularly preferred compounds of the formulae PH and BF are        selected from the group consisting of the following        sub-formulae:

-   -   in which R and R′ each, independently of one another, denote a        straight-chain alkyl or alkoxy radical having 1-7 C atoms.

-   The liquid-crystal mixture according to the invention is    dielectrically negative with a dielectric anisotropy (Δ∈) of ≦−1.5.    The compounds of the formulae IIIA, IIIB, IIIC, LY1-LY18, Y1-Y16,    T1-T24, FI, VK1-VK4, N1-N10, BC, CR, PH and BF are suitable as    dielectrically negative component. The dielectrically negative    compounds are preferably selected from the formulae IIIA, IIIB and    IIIC. The LC medium preferably has a Δ∈ of −1.5 to −8.0, in    particular −2.5 to −6.0.

The values of the birefringence Δn in the liquid-crystal mixture aregenerally between 0.07 and 0.16, preferably between 0.08 and 0.12. Therotational viscosity γ₁ at 20° C. before the polymerisation ispreferably ≦165 mPa·s, in particular ≦140 mPa·s.

Preferred embodiments of the liquid-crystalline medium having positivedielectric anisotropy according to the invention are indicated below:

-   -   LC medium which additionally comprises one or more compounds of        the formulae II and/or III:

-   -   in which    -   ring A denotes 1,4-phenylene or trans-1,4-cyclohexylene,    -   a is 0 or 1,    -   R³ in each case, independently of one another, denotes alkyl        having 1 to 9 C atoms or alkenyl having 2 to 9 C atoms,        preferably alkenyl having 2 to 9 C atoms, and    -   R⁴ in each case, independently of one another, denotes an        unsubstituted or halogenated alkyl radical having 1 to 12 C        atoms, where, in addition, one or two non-adjacent CH₂ groups        may be replaced by —O—, —CH═CH—, —CH═CF—, —(CO)—, —O(CO)— or        —(CO)O— in such a way that O atoms are not linked directly to        one another, and preferably denotes alkyl having 1 to 12 C atoms        or alkenyl having 2 to 9 C atoms.    -   The compounds of the formula II are preferably selected from the        group consisting of the following formulae:

-   -   in which R^(3a) and R^(4a) each, independently of one another,        denote H, CH₃, C₂H₅ or C₃H₇, and “alkyl” denotes a        straight-chain alkyl group having 1 to 8, preferably 1, 2, 3, 4        or 5, C atoms. Particular preference is given to compounds of        the formulae IIa and IIf, in particular those in which R^(3a)        denotes H or CH₃, preferably H, and compounds of the formula        IIc, in particular those in which R^(3a) and R^(4a) denote H,        CH₃ or C₂H₅.    -   The compounds of the formula III are preferably selected from        the group consisting of the following formulae:

-   -   in which “alkyl” and R^(3a) have the meanings indicated above,        and R^(3a) preferably denotes H or CH₃. Particular preference is        given to compounds of the formula IIIb;    -   LC medium which additionally comprises one or more compounds        selected from the group consisting of the following formulae:

-   -   in which    -   R⁰ denotes an alkyl or alkoxy radical having 1 to 15 C atoms,        where, in addition, one or more CH₂ groups in these radicals may        each be replaced, independently of one another, by —C≡C—,        —CF₂O—, —CH═CH—,

—O—, —(CO)O— or —O(CO)— in such a way that O atoms are not linkeddirectly to one another, and in which, in addition, one or more H atomsmay be replaced by halogen,

-   -   X⁰ denotes F, Cl, CN, SF₅, SCN, NCS, a halogenated alkyl        radical, halogenated alkenyl radical, halogenated alkoxy radical        or halogenated alkenyloxy radical, each having up to 6 C atoms,    -   Y¹⁻⁶ each, independently of one another, denote H or F,    -   Z⁰ denotes —C₂H₄—, —(CH₂)₄—, —CH═CH—, —CF═CF—, —C₂F₄—, —CH₂CF₂—,        —CF₂CH₂—, —CH₂O—, —OCH₂—, —COO—, —CF₂O— or —OCF₂—, in the        formulae V and VI also a single bond, and    -   b and c each, independently of one another, denote 0 or 1.    -   In the compounds of the formulae IV to VIII, X⁰ preferably        denotes F or OCF₃, furthermore OCHF₂, CF₃, CF₂H, Cl, OCH═CF₂. R⁰        is preferably straight-chain alkyl or alkenyl, each having up to        6 C atoms.    -   The compounds of the formula IV are preferably selected from the        group consisting of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above.    -   In formula IV, R⁰ preferably denotes alkyl having 1 to 8 C atoms        and X⁰ preferably denotes F, Cl, OCHF₂ or OCF₃, furthermore        OCH═CF₂. In the compound of the formula IVb, R⁰ preferably        denotes alkyl or alkenyl. In the compound of the formula IVd, X⁰        preferably denotes Cl, furthermore F.    -   The compounds of the formula V are preferably selected from the        group consisting of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above. In formula        V, R⁰ preferably denotes alkyl having 1 to 8 C atoms and X⁰        preferably denotes F;    -   LC medium which comprises one or more compounds of the formula        VI-1:

-   -   particularly preferably those selected from the group consisting        of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above. In formula        VI, R⁰ preferably denotes alkyl having 1 to 8 C atoms and X⁰        preferably denotes F, furthermore OCF₃.    -   LC medium which comprises one or more compounds of the formula        VI-2:

-   -   particularly preferably those selected from the group consisting        of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above.    -   In formula VI, R⁰ preferably denotes alkyl having 1 to 8 C atoms        and X⁰ preferably denotes F;    -   LC medium which preferably comprises one or more compounds of        the formula VII in which Z⁰ denotes —CF₂O—, —CH₂CH₂— or —(CO)O—,        particularly preferably those selected from the group consisting        of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above. In formula        VII, R⁰ preferably denotes alkyl having 1 to 8 C atoms and X⁰        preferably denotes F, furthermore OCF₃.    -   The compounds of the formula VIII are preferably selected from        the group consisting of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above. R⁰        preferably denotes a straight-chain alkyl radical having 1 to 8        C atoms. X⁰ preferably denotes F.    -   LC medium which additionally comprises one or more compounds of        the following formula:

-   -   in which R⁰, X⁰, Y¹ and Y² have the meanings indicated above,        and

each, independently of one another, denote

where the rings A and B do not both simultaneously denote cyclohexylene;

-   -   The compounds of the formula IX are preferably selected from the        group consisting of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above. R⁰        preferably denotes alkyl having 1 to 8 C atoms and X⁰ preferably        denotes F. Particular preference is given to compounds of the        formula IXa;    -   LC medium which additionally comprises one or more compounds        selected from the group consisting of the following formulae:

-   -   in which R⁰, X⁰ and Y¹⁻⁴ have the meanings indicated above, and

each, independently of one another, denote

-   -   The compounds of the formulae X and XI are preferably selected        from the group consisting of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above. R⁰        preferably denotes alkyl having 1 to 8 C atoms and/or X⁰        preferably denotes F. Particularly preferred compounds are those        in which Y¹ denotes F and Y² denotes H or F, preferably F;    -   LC medium which additionally comprises one or more compounds of        the following formula XII:

-   -   in which R⁵ and R⁶ each, independently of one another, denote        n-alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl, each having        up to 9 C atoms, and preferably each, independently of one        another, denote alkyl having 1 to 7 C atoms or alkenyl having 2        to 7 C atoms. Y¹ denotes H or F.    -   Preferred compounds of the formula XII are those selected from        the group consisting of the following formulae:

-   -   in which    -   alkyl and alkyl* each, independently of one another, denote a        straight-chain alkyl radical having 1 to 6 C atoms, and    -   alkenyl and    -   alkenyl* each, independently of one another, denote a        straight-chain alkenyl radical having 2 to 6 C atoms.    -   Very particular preference is given to compounds of the        following formula:

-   -   in which alkyl has the meaning indicated above, and R^(6a)        denotes H or CH₃.    -   LC medium which additionally comprises one or more compounds        selected from the group consisting of the following formulae:

-   -   in which R⁰, X⁰, Y¹ and Y² have the meanings indicated above. R⁰        preferably denotes alkyl having 1 to 8 C atoms and X⁰ preferably        denotes F or Cl;    -   The compounds of the formulae XIII and XIV are preferably        selected from the group consisting of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above. R⁰        preferably denotes alkyl having 1 to 8 C atoms. In the compounds        of the formula XIII, X⁰ preferably denotes F or Cl.    -   LC medium which additionally comprises one or more compounds of        the formulae D1 and/or D2:

-   -   in which Y¹, Y², R⁰ and X⁰ have the meanings indicated above. R⁰        preferably denotes alkyl having 1 to 8 C atoms and X⁰ preferably        denotes F. Particular preference is given to compounds of the        following formulae:

-   -   in which R⁰ has the meaning indicated above and preferably        denotes straight-chain alkyl having 1 to 6 C atoms, in        particular C₂H₅, n-C₃H₇ or n-C₅H₁₁.    -   LC medium which additionally comprises one or more compounds of        the following formulae:

-   -   in which Y¹, R¹ and R² have the meanings indicated above. R¹ and        R² preferably each, independently of one another, denote alkyl        having 1 to 8 C atoms. Y¹ preferably denotes F. Preferred media        comprise 1-15% by weight, in particular 1-10% by weight, of        these compounds.    -   LC medium which additionally comprises one or more compounds of        the following formula:

-   -   in which X⁰, Y¹ and Y² have the meanings indicated above, and        “alkenyl” denotes C₂₋₇-alkenyl. Particular preference is given        to compounds of the following formula:

-   -   in which R^(3a) has the meaning indicated above and preferably        denotes H;    -   LC medium which additionally comprises one or more tetracyclic        compounds selected from the group consisting of the formulae XIX        to XXV:

-   -   in which Y¹⁻⁴, R⁰ and X⁰ each, independently of one another,        have one of the meanings indicated above. X⁰ is preferably F,        Cl, CF₃, OCF₃ or OCHF₂. R⁰ preferably denotes alkyl, alkoxy,        oxaalkyl, fluoroalkyl or alkenyl, each having up to 8 C atoms.    -   LC medium which additionally comprises one or more compounds of        the following formula:

-   -   in which R⁰, X⁰ and Y¹⁻⁴ have the meanings indicated above.        Particular preference is given to compounds of the following        formula:

-   -   R⁰ is generally preferably straight-chain alkyl or alkenyl        having 2 to 7 C atoms;    -   X⁰ is preferably F, furthermore OCF₃, Cl or CF₃;    -   the medium preferably comprises one or more compounds selected        from the group of the compounds of the formula II;    -   the medium preferably comprises one or more compounds selected        from the group of the compounds of the formulae VI-2, VII-1a,        VII-1b, IX, X, XI and XXVI (CF₂O-bridged compounds); the total        content of compounds of the formulae VI-2, VII-1a, VII-1b, IX,        X, XI and XXVI is preferably 35% by weight or more, particularly        preferably 40% by weight or more and very particularly        preferably 45% by weight or more;    -   the proportion of compounds of the formulae II-XXVII in the        mixture as a whole is preferably 20 to 99% by weight;    -   the medium preferably comprises 25-80% by weight, particularly        preferably 30-70% by weight, of compounds of the formulae II        and/or III;    -   the medium preferably comprises 20-70% by weight, particularly        preferably 25-60% by weight, of compounds of the formula IIa;    -   the medium preferably comprises 2-25% by weight, particularly        preferably 3-20% by weight, of compounds selected from the group        of the compounds of the formula VI-2;    -   the medium comprises in total 2-30% by weight, particularly        preferably 3-20% by weight, of compounds of the formulae XI and        XXVII together;    -   the medium preferably comprises 1-20% by weight, particularly        preferably 2-15% by weight, of compounds of the formula XXIV;    -   the medium comprises in total 15-65% by weight, particularly        preferably 30-55% by weight, of compounds selected from the        high-polarity compounds of the formulae VI-2, X, XI and XXV        together.

The nematic phase of the dielectrically negative or positive LC mediumaccording to the invention preferably has a nematic phase in atemperature range from 10° C. or less to 60° C. or more, particularlypreferably from 0 or less to 70° C. or more.

In the present application and in the examples below, the structures ofthe liquid-crystal compounds are indicated by means of acronyms, withthe transformation into chemical formulae taking place in accordancewith Tables A and B below. All radicals C_(n)H_(2n+1) and C_(m)H_(2m+1)are straight-chain alkyl radicals having n and m C atoms respectively;n, m, z and k are integers and preferably denote 1, 2, 3, 4, 5, 6, 7, 8,9, 10, 11 or 12. The coding in Table B is self-evident. In Table A, onlythe acronym for the parent structure is indicated. In individual cases,the acronym for the parent structure is followed, separated by a dash,by a code for the substituents R^(1*), R^(2*), L^(1*) and L^(2*):

Code for R¹*, R²*, L¹*, L²*, L³* R¹* R²* L¹* L²* nm C_(n)H_(2n+1)C_(m)H_(2m+1) H H nOm C_(n)H_(2n+1) OC_(m)H_(2m+1) H H nO.mOC_(n)H_(2n+1) C_(m)H_(2m+1) H H n C_(n)H_(2n+1) CN H H nN.FC_(n)H_(2n+1) CN F H nN.F.F C_(n)H_(2n+1) CN F F nF C_(n)H_(2n+1) F H HnCl C_(n)H_(2n+1) Cl H H nOF OC_(n)H_(2n+1) F H H nF.F C_(n)H_(2n+1) F FH nF.F.F C_(n)H_(2n+1) F F F nOCF₃ C_(n)H_(2n+1) OCF₃ H H nOCF₃.FC_(n)H_(2n+1) OCF₃ F H n-Vm C_(n)H_(2n+1) —CH═CH—C_(m)H_(2m+1) H H nV-VmC_(n)H_(2n+1)—CH═CH— —CH═CH—C_(m)H_(2m+1) H H

Preferred mixture components are found in Tables A and B.

TABLE A

TABLE B n, m, z, independently of one another, preferably denote 1, 2,3, 4, 5 or 6.

In a preferred embodiment of the present invention, the LC mediaaccording to the invention comprise one or more compounds selected fromthe group consisting of compounds from Tables A and B.

TABLE C Table C indicates possible chiral dopants which can be added tothe LC media according to the invention.

C15

CB 15

CM 21

R/S-811

CM 44

CM 45

CM 47

CN

R/S-2011

R/S-3011

R/S-4011

R/S-5011

R/S-1011

The LC media optionally comprise 0 to 10% by weight, in particular 0.01to 5% by weight, particularly preferably 0.1 to 3% by weight, ofdopants, preferably selected from the group consisting of compounds fromTable C.

TABLE D Table D indicates possible stabilisers which can be added to theLC media according to the invention. (n here denotes an integer from 1to 12, preferably 1, 2, 3, 4, 5, 6, 7 or 8, terminal methyl groups arenot shown).

The LC media preferably comprise 0 to 10% by weight, in particular 1 ppmto 5% by weight, particularly preferably 1 ppm to 1% by weight, ofstabilisers. The LC media preferably comprise one or more stabilisersselected from the group consisting of compounds from Table D.

TABLE E Table E shows illustrative compounds which can be used in the LCmedia in accordance with the present invention, preferably as reactivecompounds.

RM-1

RM-2

RM-3

RM-4

RM-5

RM-6

RM-7

RM-8

RM-9

RM-10

RM-11

RM-12

RM-13

RM-14

RM-15

RM-16

RM-17

RM-18

RM-19

RM-20

RM-21

RM-22

RM-23

RM-24

RM-25

RM-26

RM-27

RM-28

In a preferred embodiment of the present invention, the mesogenic mediacomprise one or more compounds selected from the group of the compoundsfrom Table E.

In the present application, the term “compounds”, also written as“compound(s)”, denotes, unless explicitly indicated otherwise, both oneand also a plurality of compounds. Conversely, the term “compound”generally also encompasses a plurality of compounds, if this is possibleaccording to the definition and is not indicated otherwise. The sameapplies to the terms LC media and LC medium. The term “component” ineach case encompasses one or more substances, compounds and/orparticles.

In addition, the following abbreviations and symbols are used:

-   n_(e) extraordinary refractive index at 20° C. and 589 nm,-   n_(o) ordinary refractive index at 20° C. and 589 nm,-   Δn optical anisotropy at 20° C. and 589 nm,-   ∈_(⊥) dielectric permittivity perpendicular to the director at    20° C. and 1 kHz,-   ∈_(∥) dielectric permittivity parallel to the director at 20° C. and    1 kHz,-   Δ∈ dielectric anisotropy at 20° C. and 1 kHz,-   cl.p., T(N,I) clearing point [° C.],-   γ₁ rotational viscosity at 20° C. [mPa·s],-   K₁ elastic constant, “splay” deformation at 20° C. [pN],-   K₂ elastic constant, “twist” deformation at 20° C. [pN],-   K₃ elastic constant, “bend” deformation at 20° C. [pN].

Unless explicitly noted otherwise, all concentrations in the presentapplication are quoted in percent by weight and relate to thecorresponding mixture as a whole comprising all solid orliquid-crystalline components, without solvents.

All physical properties are and have been determined in accordance with“Merck Liquid Crystals, Physical Properties of Liquid Crystals”, StatusNov. 1997, Merck KGaA, Germany, and apply for a temperature of 20° C.,and Δn is determined at 589 nm and Δ∈ at 1 kHz, unless explicitlyindicated otherwise in each case.

The polymerisable compounds are polymerised in the display or test cellby irradiation with UVA light (usually 365 nm) of defined intensity fora pre-specified time, with a voltage optionally being appliedsimultaneously to the display (usually 10 to 30 V alternating current, 1kHz). In the examples, unless indicated otherwise, a 100 mW/cm² mercuryvapour lamp is used, and the intensity is measured using a standard UVmeter (Ushio UNI meter) fitted with a 320 nm band-pass filter.

The following examples explain the present invention without intendingto restrict it in any way. However, the physical properties make clearto the person skilled in the art what properties can be achieved and inwhat ranges they can be modified. In particular, the combination of thevarious properties which can preferably be achieved is thus well definedfor the person skilled in the art.

Further combinations of the embodiments and variants of the invention inaccordance with the description also arise from the claims.

EXAMPLES

The compounds employed, if not commercially available, are synthesisedby standard laboratory procedures. The LC media originate from MerckKGaA, Germany.

Synthesis Examples Example 1:N-[2-(2′-fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-yloxy)ethyl]-ethane-1,2-diamine1.1 4-Bromo-3-fluoro-4′-methoxybiphenyl

49.0 g (0.163 mol) of 1-bromo-2-fluoro-4-iodobenzene and 24.7 g (0.163mol) of 4-methoxybenzeneboronic acid are dissolved in a mixture of 325ml of toluene, 165 ml of water and 165 ml of ethanol, and, afteraddition of 1.9 g (1.64 mmol) of tetrakis(triphenylphosphine)palladiumand 34.9 g (0.33 mol) of sodium carbonate, the mixture is heated underreflux overnight. The org. phase is separated off, dried over sodiumsulfate and evaporated. The residue is filtered through silica gel withheptane/toluene (1:1), and the crude product is recrystallised fromethanol, giving 4-bromo-3-fluoro-4′-methoxybiphenyl as a colourlesssolid.

1.2 2′-Fluoro-4″-methoxy-4-propyl-[1,1′;4′,1″]terphenyl

28.0 g (99.0 mmol) of 4-bromo-3-fluoro-4′-methoxybiphenyl, 28.8 g (99.2mmol) of sodium metaborate octahydrate and 1.4 g (1.96 mmol) ofbis(triphenylphosphine)palladium(II) chloride are initially introducedin 75 ml of water and 100 ml of THF, 0.1 ml of hydrazine hydrate isadded, and, after addition of a solution of 16.3 g (99.0 mmol) of4-propylbenzeneboronic acid, the mixture is heated under refluxovernight. The org. phase is separated off, evaporated in vacuo,filtered through silica gel with heptane/toluene, and the crude productis recrystallised from ethanol/toluene (14:1), giving2′-fluoro-4″-methoxy-4-propyl-[1,1′;4′,1″]terphenyl as colourlesscrystals.

1.3 2′-Fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-ol

27.2 g (85 mmol) of 2′-fluoro-4″-methoxy-4-propyl-[1,1′;4′,1″]terphenylare initially introduced in 400 ml of dichloromethane at −10° C., and100 ml (100 mmol) of a 1 M solution of boron tribromide in hexane areadded dropwise. The cooling is removed, and the batch is left to stir atroom temp. for 3 h. The batch is subsequently hydrolysed using 200 ml ofwater with cooling, the precipitated product is dissolved by addition of800 ml of warm dichloromethane, and the aqueous phase is separated off.The org. phase is washed with water and sat. sodium hydrogencarbonatesoln. and dried over sodium sulfate, giving2′-fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-ol as a colourless solid,which is employed in the next step without further purification.

1.4 4″-(2-Benzyloxyethoxy)-2′-fluoro-4-propyl-[1,1′;4′,1″]terphenyl

The crude product from step 1.4 is dissolved in 300 ml of ethyl methylketone, 23.9 g (173 mmol) of potassium carbonate and 20.0 g (90 mmol) of2-benzyloxyethyl bromide are added, and the mixture is heated underreflux overnight. The batch is filtered, the filtrate is evaporated, andthe residue is filtered through silica gel with toluene. Crystallisationof the crude product from ethanol/toluene (6:1) gives4″-(2-benzyloxyethoxy)-2′-fluoro-4-propyl-[1,1′;4′,1″]terphenyl as acolourless solid.

1.5 2-(2′-Fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-yloxy)ethanol

24.5 g (56 mmol) of4″-(2-benzyloxyethoxy)-2′-fluoro-4-propyl-[1,1′;4′,1″]terphenyl arehydrogenated to completion on palladium/carbon in THF. The catalyst isfiltered off, the filtrate is evaporated, and the crude product isrecrystallised from ethanol/toluene (8:1), giving2-(2′-fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-yloxy)ethanol ascolourless needles.

1.6 2-(2′-Fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-yloxy)ethyltoluene-4-sulfonate

7.0 g (20 mmol) of2-(2′-fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-yloxy)ethanol aredissolved in 200 ml of dichloromethane, 3.3 ml (40 mmol) of pyridine and120 mg of DMAP are added, and the mixture is cooled to 10° C. Afteraddition of 4.6 g (24 mmol) of tosyl chloride, the batch is stirred atroom temperature overnight, and 500 ml of water are subsequently added.The aqueous phase is separated off and extracted with dichloromethane.The combined org. phases are washed with dil. hydrochloric acid and withsat. sodium hydrogencarbonate solution and dried over sodium sulfate.The solvent is removed in vacuo, and the residue is purified bychromatography on silica gel with toluene, giving2-(2′-fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-yloxy)ethyltoluene-4-sulfonate as a colourless solid.

1.7N-[2-(2′-Fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-yloxy)ethyl]ethane-1,2-diamine

1.00 g (1.98 mmol) of2-(2′-fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-yloxy)ethyltoluene-4-sulfonate is warmed at 60° C. overnight in 20 ml ofethylenediamine. The amine is subsequently removed in vacuo, and theresidue is filtered through silica gel with dichloromethane/methanol/25percent ammonia (80:20:2), givingN-[2-(2′-fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-yloxy)ethyl]ethane-1,2-diamineas a colourless solid.

¹H-NMR (300 MHz, CDCl₃)

δ=0.98 ppm (t, J=7.4 Hz, 3H, CH₃), 1.56 (s, br., 2H, NH₂), 1.69 (sext.,J=7.4 Hz, 2H, CH₂CH₂CH₃), 2.64 (t, J=7.4 Hz, 2H, —CH₂Et), 2.76 (t, J=5.8Hz, 2H, —CH₂NH₂), 2.85 (t, J=5.8 Hz, 2H, CH₂—CH₂NH₂), 3.05 (t, J=5.2 Hz,2H, OCH₂CH₂—), 4.13 (t, J=5.8 Hz, 2H, —OCH₂—), 6.99 (AB-d, J=8.7 Hz, 2H,Ar—H), 7.26 (d, J=8.5 Hz, 2H, Ar—H), 7.33 (dd, J=1.7 Hz, J=12.1 Hz, 1H,Ar—H), 7.38 (dd, J=1.7 Hz, J=8.0 Hz, 1H, Ar—H), 7.50 (m_(e), 2 H, Ar—H),7.54 (AB-d, J=8.7 Hz, 2H, Ar—H).

Example 2:N-[2-(2′-fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-yloxy)ethyl]-propane-1,3-diamine

Analogously to Example 1,2-(2′-fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-yloxy)ethyltoluene-4-sulfonate and 1,3-diaminopropane giveN-[2-(2′-fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-yloxy)ethyl]propane-1,3-diamine.

¹H-NMR (300 MHz, CDCl₃)

δ=0.98 ppm (t, J=7.3 Hz, 3H, CH₃), 1.55-1.90 (m, 6H, in which: 1.67(quint., J=7.1 Hz, —NH—CH₂—CH₂—CH₂NH₂); s, br., NH2; CH₃CH₂CH₂—), 2.63(dd, J=7.3 Hz, J=8.0 Hz, 2H, Ar—CH₂Et), 2.75 (t, J=7.1 Hz, 2H, —CH₂NH₂),2.78 (t, J=6.9 Hz, 2H, —NH—CH₂—(CH₂)₂NH₂), 3.01 (t, J=5.3 Hz, 2H,—OCH₂CH₂—NH), 3.41 (s, 1H, —NH—), 4.11 (t, J=5.3 Hz, 2H, —O—CH₂—), 6.98(AB-d, J=8.8 Hz, 2H, Ar—H), 7.26 (d, J=8.2 Hz, 2H, Ar—H), 7.32 (dd,J=1.8 Hz, J=12.2 Hz, 1H, Ar—H), 7.37 (dd, J=1.8 Hz, J=8.0 Hz, 1H, Ar—H),7.43-7.56 (m, 5H, Ar—H).

Example 3:[2-(2′-fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-yloxy)ethyl]-(2-methoxyethyl)amine

Analogously to Example 1,2-(2′-fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-yloxy)ethyltoluene-4-sulfonate and 2-methoxy-1-ethylamine give[2-(2′-fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-yloxy)ethyl]-(2-methoxyethyl)amineas a colourless solid.

¹H-NMR (400 MHz, CDCl₃)

δ=0.98 ppm (t, J=7.3 Hz, 3H, CH₃), 1.69 (sext., J=7.5 Hz, 2H,CH₃CH₂CH₂—), 1.74 (s, br., NH), 2.64 (dd, J=6.7 Hz, J=8.6 Hz, 2H,—CH₂—Et), 2.89 (t, J=5.3 Hz, 2H, —CH₂—NH—), 3.06 (t, 5.3 Hz, 2H,—CH₂—NH—), 3.38 (s, 3H, OCH₃), 3.54 (dd, J=5.3, J=5.3 Hz, 2H, —O—CH₂—),4.13 (t, 5.3 Hz, 2H, —O—CH₂—), 7.00 (AB-d, J=8.7 Hz, 2H, Ar—H), 7.26 (d,J=8.3 Hz, 2H, Ar—H), 7.32 (dd, J=1.7 Hz, J=12.2 Hz, 1H, Ar—H), 7.39 (dd,J=1.8 Hz, J=8.0 Hz, 1H, Ar—H), 7.44-7.57 (m, 5H, Ar—H).

Example 4:2′-fluoro-4″-[2-(2-methoxyethoxy)ethoxy]-4-propyl-[1,1′;4′,1″]-terphenyl

735 mg (18.4 mmol) of a 60 percent dispersion of sodium hydride inmineral oil are washed with pentane under nitrogen and dried in vacuo.30 ml of THF and 1.21 g (15.9 mmol) of ethylene glycol monomethyl etherare subsequently added, and the mixture is left to stir at room temp.until the evolution of gas is complete. After addition of a solution of5.00 g (12.2 mmol) of2-(2′-fluoro-4-propyl-[1,1′;4′,1″]terphenyl-4″-yloxy)ethyltoluene-4-sulfonate in 10 ml of THF, the batch is left to stir at roomtemperature for 3 d, and excess sodium hydride is then decomposed byaddition of methanol. The solution is added to water, acidified using 2M hydrochloric acid and extracted three times with MTB ether. Thecombined org. phases are dried over sodium sulfate and evaporated invacuo. The crude product is filtered through silica gel withdichloromethane and recrystallised from toluene, giving2′-fluoro-4″-[2-(2-methoxyethoxy)ethoxy]-4-propyl-[1,1′;4′,1″]terphenylas colourless crystals.

Example 5:N-{2-[(3S,5S,8R,9S,10S,13R,14S,17R)-17-((R)-1,5-dimethylhexyl)-10,13-dimethylhexadecahydrocyclopenta[a]phenanthren-3-yloxy]-ethyl}ethane-1,2-diamine5.1tert-Butyl-{2-[(3S,5S,8R,9S,10S,13R,14S,17R)-17-((R)-1,5-dimethylhexyl)-10,13-dimethylhexadecahydrocyclopenta[a]phenanthren-3-yloxy]ethoxy}dimethylsilane

1.15 g (28.8 mmol) of a 60 percent suspension of sodium hydride inparaffin oil are initially introduced in 70 ml of THF, and a solution of9.0 g (23.2 mmol) of(3S,5S,8R,9S,10S,13R,14S,17R)-17-((R)-1,5-dimethylhexyl)-10,13-dimethylhexadecahydrocyclopenta[a]phenanthren-3-olin 60 ml of THF is added dropwise. The batch is heated at 70° C. for 2h, a solution of 10 ml (49 mmol) of(2-bromoethoxy)-tert-butyldimethylsilane in 50 ml of THF is added, andthe mixture is stirred at 70° C. overnight. The mixture is subsequentlyhydrolysed using 300 ml of water and extracted three times with MTBether. The combined org. phases are washed with water and dried oversodium sulfate. The solvent is removed in vacuo, and the residue ischromatographed on silica gel with toluene, givingtert-butyl-{2-[(3S,5S,8R,9S,10S,13R,14S,17R)-17-((R)-1,5-dimethylhexyl)-10,13-dimethylhexadecahydrocyclopenta[a]phenanthren-3-yloxy]ethoxy}dimethylsilaneas colourless crystals.

5.22-[(3S,5S,8R,9S,10S,13R,14S,17R)-17-((R)-1,5-Dimethylhexyl)-10,13-dimethylhexadecahydrocyclopenta[a]phenanthren-3-yloxy]ethanol

1.90 g (3.47 mmol) oftert-butyl-{2-[(3S,5S,8R,9S,10S,13R,14S,17R)-17-((R)-1,5-dimethylhexyl)-10,13-dimethylhexadecahydrocyclopenta[a]phenanthren-3-yloxy]ethoxy}dimethylsilaneare dissolved in 20 ml of THF, and 3.8 ml (38 mmol) of a 1 M solution oftetrabutylammonium fluoride in THF are added dropwise with ice cooling.The cooling is removed, the batch is left to stir at room temp. for 15min and added to water. The aqueous phase is separated off and extractedwith MTB ether. The combined org. phases are washed with sat. sodiumchloride soln., dried over sodium sulfate, and the solvent is removed invacuo, giving2-[(3S,5S,8R,9S,10S,13R,14S,17R)-17-((R)-1,5-dimethylhexyl)-10,13-dimethylhexadecahydrocyclopenta[a]phenanthren-3-yloxy]ethanolas a viscous yellow oil, which is employed in the next step withoutfurther purification.

5.32-[(3S,5S,8R,9S,10S,13R,14S,17R)-17-((R)-1,5-Dimethylhexyl)-10,13-dimethylhexadecahydrocyclopenta[a]phenanthren-3-yloxy]ethyltoluene-4-sulfonate

Analogously to Example 1,2-[(3S,5S,8R,9S,10S,13R,14S,17R)-17-((R)-1,5-dimethylhexyl)-10,13-dimethylhexadecahydrocyclopenta[a]phenanthren-3-yloxy]ethanolgives2-[(3S,5S,8R,9S,10S,13R,14S,17R)-17-((R)-1,5-dimethylhexyl)-10,13-dimethylhexadecahydrocyclopenta[a]phenanthren-3-yloxy]ethyltoluene-4-sulfonate as a viscous oil.

5.4N-{2-[(3S,5S,8R,9S,10S,13R,14S,17R)-17-((R)-1,5-Dimethylhexyl)-10,13-dimethylhexadecahydrocyclopenta[a]phenanthren-3-yloxy]ethyl}-ethane-1,2-diamine

Analogously to Example 1,2-[(3S,5S,8R,9S,10S,13R,14S,17R)-17-((R)-1,5-dimethylhexyl)-10,13-dimethylhexadecahydrocyclopenta[a]phenanthren-3-yloxy]ethyltoluene-4-sulfonate givesN-{2-[(3S,5S,8R,9S,10S,13R,14S,17R)-17-((R)-1,5-dimethylhexyl)-10,13-dimethylhexadecahydrocyclopenta[a]phenanthren-3-yloxy]ethyl}ethane-1,2-diamineas a colourless viscous oil.

¹H-NMR (500 MHz, CDCl₃)

δ=0.65 (s, 3H, —CH₃), 0.75-0.89 (m, 46H, in which: 0.79 (s, 3H, —CH₃),0.86 (d, J=2.1 Hz, 3H, —CH₃), 0.87 (d, J=2.1 Hz, 3H, —CH₃), 0.90 (d,J=6.5 Hz, 3H, —CH₃), alkyl-H, —NH—, —NH₂), 1.96 (ddd, J=12.6 Hz, J=3.2Hz, J=3.2 Hz, 1H), 2.69 (t, J=6.0 Hz, 2H, —CH₂NH₂), 2.77 (dd, J=5.4 Hz,J=5.4 Hz, 2H, —OCH₂CH₂NH—), 2.81 (t, J=6.0 Hz, 2H, —NHCH₂CH₂NH₂), 3.22(dddd, J=4.7 Hz, J=4.7 Hz, J=4.7 Hz, J=4.7 Hz, 1H, >CH—O—), 3.58 (m_(e),2 H, —CH₂O—).

The following compounds for use in LC media are prepared analogously orin accordance with a literature procedure (in some cases alsocommercially available):

Example No. Structural formula  6.

 7.

 8.

 9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

Mixture Examples

For the preparation of LC media according to the invention, thefollowing liquid-crystalline mixtures consisting of low-molecular-weightcomponents in the stated percentage proportions by weight are used.

TABLE 1 Nematic LC medium M1 (Δε < 0) CY-3-O4 14%  Cl.p. +80° C.CCY-3-O2 9% Δn 0.090 CCY-3-O3 9% Δε −3.3 CPY-2-O2 10%  ε_(||) 3.4CPY-3-O2 10%  K₃/K₁ 0.97 CCY-3-1 8% CCH-34 9% CCH-35 6% PCH-53 10% CCH-301 6% CCH-303 9%

TABLE 2 Nematic LC medium M2 (Δε > 0) CC-4-V 10% Cl.p. +77° C. CC-5-V13.5%  Δn 0.113 PGU-3-F 6.5%  Δε 19.2 ACQU-2-F 10% ε_(||) 23.8 ACQU-3-F12% K₃/K₁ 0.97 PUQU-3-F 11% CCP-V-1 12% APUQU-2-F  6% APUQU-3-F  7%PGUQU-3-F  8% CPGU-3-OT  4%

Mixture Example 1

The compound from Synthesis Example 5 (0.2% by weight) is added to anematic LC medium M1 of the VA type (Δ∈<0) as shown in Table 1, and themixture is homogenised.

Use in test cells without pre-alignment layer:

The resultant mixture is introduced into a test cell (without polyimidealignment layer, layer thickness d≈4.0 μm, ITO coating on both sides, nopassivation layer). The LC medium has spontaneous homeotropic (vertical)alignment to the substrate surfaces. This alignment remains stable up to70° C. In the temperature-stable range, the VA cell can be switchedreversibly between crossed polarisers by application of a voltage ofbetween 0 and 30 V.

Mixture Example 2

The compound from Synthesis Example 5 (0.5% by weight) is added to anematic LC medium M2 of the VA-IPS type (Δ∈>0) as shown in Table 2, andthe mixture is homogenised.

Use in test cells without pre-alignment layer:

The resultant mixture is introduced into a test cell (without polyimidealignment layer, layer thickness d≈10 μm, ITO interdigital electrodesarranged on a substrate surface, glass on the opposite substratesurface, no passivation layer). The LC medium has spontaneoushomeotropic (vertical) alignment to the substrate surfaces. Thisalignment remains stable up to 70° C. In the temperature-stable range,the VA-IPS cell can be switched reversibly between crossed polarisers byapplication of a voltage of between 0 and 20 V.

Mixture Examples 3-17

The compounds of Synthesis Examples 1, 2, 3 and Examples 6-17 are addedanalogously to Mixture Example 1 to a nematic LC medium M1 (Δ∈<0) asshown in Table 1, and the mixture is homogenised. The proportions byweight of the compounds in the medium are indicated in Table 3. Theresultant LC medium is in each case introduced into a test cell withoutpre-alignment layer and has spontaneous homeotropic (vertical) alignmentto the substrate surfaces. In the temperature-stable range, the VA cellcan be switched reversibly between crossed polarisers by application ofa voltage of between 0 and 30 V.

TABLE 3 Proportions by weight for doping in M1 and alignment of theresultant LC mixture at 25° C. and 70° C. Test cell of the VA typeMixture Compound Exam- Example Proportion Alignment at Alignment at pleNo. by weight 25° C./switchable 70° C./switchable 3 1 0.25% homeotropic/yes homeotropic/yes 4 2 0.15%  homeotropic/yeshomeotropic/yes 5 3 5.0% homeotropic/yes homeotropic/yes 6 6 1.0%homeotropic/yes homeotropic/yes 7 7 1.5% homeotropic/yes homeotropic/yes8 8 2.5% homeotropic/yes homeotropic/yes 9 9 2.5% homeotropic/yeshomeotropic/yes 10 10 2.5% homeotropic/yes homeotropic/yes 11 11 2.5%homeotropic/yes homeotropic/yes 12 12 0.5% homeotropic/yeshomeotropic/yes 13 13 0.5% homeotropic/yes homeotropic/yes 14 14 2.0%homeotropic/yes homeotropic/yes 15 15 0.7% homeotropic/yeshomeotropic/yes 16 16 1.0% homeotropic/yes homeotropic/yes 17 17 2.0%homeotropic/yes homeotropic/yes 18 18 2.0% homeotropic/yes 19 19 2.0%homeotropic/yes 20 20 1.0% homeotropic/yes 21 21 0.7% homeotropic/yes 2222 0.5% homeotropic/yes

Mixture Examples 22-26

The compounds of Synthesis Example 1 and Examples 6, 7, 10, 11 are addedanalogously to Mixture Example 2 to a nematic LC medium M2 (Δ∈>0) asshown in Table 2, and the mixture is homogenised. The proportions byweight of the compounds in the medium are indicated in Table 4. Theresultant LC medium is in each case introduced into a test cell withoutpre-alignment layer and has spontaneous homeotropic (vertical) alignmentto the substrate surfaces. In the temperature-stable range, the VA-IPScell can be switched reversibly between crossed polarisers byapplication of a voltage of between 0 and 20 V.

TABLE 4 Proportions by weight for doping in M2 and alignment of theresultant LC mixture at 25° C. and 60° C. Test cell of the VA-IPS typeMixture Exam- Compound ple Example Proportion Alignment at Alignment atNo. No. by weight 25° C./switchable 60° C./switchable 22 1 0.5%homeotropic/yes homeotropic/yes 23 6 3.0% homeotropic/yes planar 24 71.0% homeotropic/yes homeotropic/yes 25 10 1.7% homeotropic/yes planar26 11 2.5% homeotropic/yes planar 27 18 2.0% homeotropic/yes 28 19 2.0%homeotropic/yes 29 20 1.0% homeotropic/yes 30 21 0.7% homeotropic/yes 3122 0.5% homeotropic/yes

Mixture Example 32 (Polymer Stabilisation of Mixture Example 6)

A polymerisable compound (RM-1, 0.5% by weight) and a self-aligningcompound (6, 1.0% by weight) are added to a nematic LC medium M1 (Δ∈<0)as shown in Table 1, and the mixture is homogenised.

Use in test cells without pre-alignment layer:

The resultant mixture is introduced into a test cell (without polyimidealignment layer, layer thickness d≈4.0 μm, ITO coating on both sides, nopassivation layer). The LC medium has spontaneous homeotropic (vertical)alignment to the substrate surfaces. The cell is irradiated with UVlight of intensity 100 mW/cm² at 40° C. for 15 min with application of avoltage greater than the optical threshold voltage. This causespolymerisation of the monomeric, polymerisable compound. The homeotropicalignment is thus additionally stabilised, and a pretilt is established.The resultant PSA-VA cell can be switched reversibly at up to 70° C.with application of a voltage of between 0 and 30 V. The response timesare shortened compared with the unpolymerised cell.

Mixture Example 33 (Polymer Stabilisation of Mixture Example 7)

A polymerisable compound (RM-1, 0.5% by weight) and a self-aligningcompound (7, 1.7% by weight) are added to a nematic LC medium M1 (Δ∈<0)as shown in Table 1, and the mixture is homogenised.

Use in test cells without pre-alignment layer:

The resultant mixture is introduced into a test cell (without polyimidealignment layer, layer thickness d≈4.0 μm, ITO coating on both sides, nopassivation layer). The LC medium has spontaneous homeotropic (vertical)alignment to the substrate surfaces. The cell is irradiated with UVlight of intensity 100 mW/cm² at 40° C. for 15 min with application of avoltage greater than the optical threshold voltage. This causespolymerisation of the monomeric compound. The homeotropic alignment isthus additionally stabilised, and a pretilt is established. Theresultant PSA-VA cell can be switched reversibly at up to 70° C. byapplication of a voltage of between 0 and 30 V. The response times areshortened compared with the unpolymerised cell.

1. A LC medium comprising a low-molecular-weight liquid-crystallinecomponent and one or more organic compounds, where the organic compoundcontains at least one polar anchor group and at least one ring group,the polar anchor group of the organic compound contains at least one OHstructure or an N atom in a primary or secondary or tertiary aminogroup, and wherein the anchor group is not comprised of a OH group whichis a screened OH group as in 2,6-di-tert-butylphenol, said LC mediumbeing nematic.
 2. The LC medium according to claim 1, additionallycomprising a polymerizable or polymerized component, where thepolymerized component is obtainable by polymerization of a polymerizablecomponent.
 3. The LC medium according to claim 1, wherein the organiccompound has a relative molar mass of greater than 100 g/mol.
 4. The LCmedium according to claim 1, wherein the polar anchor group of theorganic compound denotes a group of the formula R², where R² denotesstraight-chain, branched or cyclic alkyl having 1 to 25 C atoms, inwhich, in addition, one or more non-adjacent CH₂ groups may be replacedby —NR⁰, —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— in such a way that N,O and/or S atoms are not linked directly to one another, and in which,in addition, one or more tertiary carbon atoms (CH groups) may bereplaced by N, and in which, in addition, one or more H atoms may bereplaced by F or Cl, with the proviso that the radical R² contains oneor more heteroatoms selected from N, S and/or O.
 5. (canceled)
 6. The LCmedium according claim 1, wherein organic compound encompasses acompound of the formula MES-R², in which MES denotes a mesogenic groupcontaining at least one ring system, and R² denotes a polar anchorgroup.
 7. The LC medium according to claim 1, wherein the organiccompound encompasses a compound of the formula I:R¹-A¹-(Z²-A²)_(m1)-R²  (I) in which A¹ and A² each, independently of oneanother, denote an aromatic, heteroaromatic, alicyclic or heterocyclicgroup, which may also contain fused rings, and which may also be mono-or polysubstituted by a group L, L in each case, independently of oneanother, denotes —OH, —(CH₂)_(n1)—OH, F, Cl, Br, I, —CN, —NO₂, —NCO,—NCS, —OCN, —SCN, —C(═O)N(R⁰)₂, —C(═O)R⁰, —N(R⁰)₂, —(CH₂)_(n1)—N(R⁰)₂,optionally substituted silyl, optionally substituted aryl or cycloalkylhaving 6 to 20 C atoms, or straight-chain or branched alkyl, alkoxy,alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxyhaving 1 to 25 C atoms, in which, in addition, one or more H atoms maybe replaced by F or Cl, Z² in each case, independently of one another,denotes —O—, —S—, —CO—, —CO—O—, —OCO—, —O—CO—O—, —OCH₂—, —CH₂O—, —SCH₂—,—CH₂S—, —CF₂O—, —OCF₂—, —CF₂S—, —SCF₂—, —(CH₂)_(n1)—, —CF₂CH₂—,—CH₂CF₂—, —(CF₂)_(n1)—, —CH═CH—, —CF═CF—, —C≡C—, —CH═CH—COO—,—OCO—CH═CH—, CR⁰R⁰⁰ or a single bond, R⁰ and R⁰⁰ each, independently ofone another, denote H or alkyl having 1 to 12 C atoms, R¹, R²,independently of one another, denote H, halogen, straight-chain,branched or cyclic alkyl having 1 to 25 C atoms, in which, in addition,one or more non-adjacent CH₂ groups may be replaced by —NR⁰—, —O—, —S—,—CO—, —CO—O—, —O—CO—, —O—CO—O— in such a way that N, O and/or S atomsare not linked directly to one another, and in which, in addition, oneor more tertiary carbon atoms (CH groups) may be replaced by N, and inwhich, in addition, one or more H atoms may be replaced by F or Cl, withthe proviso that at least the radical R² contains one or moreheteroatoms selected from N, S and/or O, m1 denotes 0, 1, 2, 3, 4 or 5,and n1 denotes 1, 2, 3 or
 4. 8. The LC medium according to claim 7,wherein Z² denotes a single bond.
 9. The LC medium according to claim 6,wherein the group R² encompasses a group of the sub-formula (A1)-Sp-[X²—Z³-]_(k)X¹  (A1) in which Sp denotes a spacer group or a singlebond, X¹ denotes a group —NH₂, —NHR¹¹, —NR¹¹ ₂, —OH, —(CO)OH or a groupof the formula

R⁰ denotes H or alkyl having 1 to 12 C atoms, X² in each caseindependently denotes —NH—, —NR¹¹—, —O— or a single bond, Z³ in eachcase independently denotes an alkylene group having 1-15 C atoms,carbocyclic rings having 5 or 6 C atoms, or combinations of one or morerings and alkylene groups, in each of which hydrogen may be replaced by—OH, —OR¹¹, —(CO)OH, —NH₂, —NHR¹¹, —NR¹¹ ₂ or halogen (preferably F,Cl), R¹¹ in each case independently denotes a halogenated orunsubstituted alkyl radical having 1 to 15 C atoms, where, in addition,one or more CH₂ groups in this radical may each be replaced,independently of one another, by —C≡C—, —CH═CH—, —(CO)O—, —O(CO)—,—(CO)— or —O— in such a way that O atoms are not linked directly to oneanother, and where two radicals R¹¹ may be linked to one another to forma ring, and k denotes 0, 1, 2 or
 3. 10. The LC medium according to claim7, comprising the compounds of the formula I in a concentration of lessthan 10% by weight.
 11. The LC medium according to claim 2, wherein thepolymerizable or polymerized component is one or more polymerizablecompounds of the formula M or a polymerized component which comprisesone or more compounds of the formula M in polymerized form:P^(a)-(Sp^(a))_(s1)-A²-(Z¹-A¹)_(n)-(Sp^(b))_(s2)-P^(b)  M in which theindividual radicals have the following meanings: P^(a) P^(b) each,independently of one another, denote a polymerizable group, Sp^(a),Sp^(b) on each occurrence, identically or differently, denote a spacergroup, s1, s2 each, independently of one another, denote 0 or 1, A¹, A²each, independently of one another, denote a radical selected from thefollowing groups: a) the group consisting of trans-1,4-cyclohexylene,1,4-cyclohexenylene and 4,4′-bicyclohexylene, in which, in addition, oneor more non-adjacent CH₂ groups may be replaced by —O— and/or —S— and inwhich, in addition, one or more H atoms may be replaced by F, b) thegroup consisting of 1,4-phenylene and 1,3-phenylene, in which, inaddition, one or two CH groups may be replaced by N and in which, inaddition, one or more H atoms may be replaced by L, c) the groupconsisting of tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diyl,tetrahydrofuran-2,5-diyl, cyclobutane-1,3-diyl, piperidine-1,4-diyl,thiophene-2,5-diyl and selenophene-2,5-diyl, each of which may also bemono- or polysubstituted by L, d) the group consisting of saturated,partially unsaturated or fully unsaturated, and optionally substituted,polycyclic radicals having 5 to 20 cyclic C atoms, one or more of whichmay, in addition, be replaced by heteroatoms, where, in addition, one ormore H atoms in these radicals may be replaced by L, n denotes 0, 1, 2or 3, Z¹ in each case, independently of one another, denotes —CO—O—,—O—CO—, —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂—, or —(CH₂)_(n)—, where n is 2, 3or 4, —O—, —CO—, —C(R^(c)R^(d))—, —CH₂CF₂—, —CF₂CF₂— or a single bond,and R^(c)R^(d) are both independently H or C₁₋₆-alkyl. L on eachoccurrence, identically or differently, denotes F, Cl, CN, SCN, SF₅ orstraight-chain or branched, in each case optionally fluorinated, alkyl,alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy oralkoxycarbonyloxy having 1 to 12 C atoms.
 12. The LC medium according toclaim 7, wherein the compound of the formula I contains one or morepolymerisable groups.
 13. A LC display comprising an LC cell having twosubstrates and at least two electrodes, where at least one substrate istransparent to light and at least one substrate has one or twoelectrodes, and a layer of an LC medium according to claim 7 locatedbetween the substrates, where the organic compound or the compound ofthe formula I is suitable for effecting homeotropic alignment of the LCmedium with respect to the substrate surfaces.
 14. The LC displayaccording to claim 13, wherein the substrates have no alignment layersfor homeotropic alignment.
 15. The LC display according to claim 13,wherein the substrates have unrubbed alignment layers on one or bothsides.
 16. The LC display according to claim 13, that is a VA displaycontaining an LC medium having negative dielectric anisotropy andelectrodes arranged on opposite substrates.
 17. The LC display accordingto claim 13, that is a VA-IPS display containing an LC medium havingpositive dielectric anisotropy and interdigital electrodes arranged onat least one substrate.
 18. A process for the preparation of an LCmedium, comprising mixing one or more organic compounds containing atleast one polar anchor group and at least one ring group or one or morecompounds of the formula I according to claim 7 are mixed with alow-molecular-weight liquid-crystalline component, and optionally addingone or more polymerizable compounds and/or additives.
 19. A compound offormula IR¹-A¹-(Z²-A²)_(m1)-R²  (I) in which: R² denotes a group of the formula(A2)

in which Sp denotes a spacer group or a single bond, X¹ denotes a group—NH₂, —NHR¹¹, —NR¹¹ ₂, —OH, —(CO)OH or a group of the formula

R⁰ denotes H or alkyl having 1 to 12 C atoms, X² in each caseindependently denotes —NH—, —NR¹¹—, —O— or a single bond, R¹² denotes H,F, Cl, CN, —OH, —NH₂, or a halogenated or unsubstituted alkyl radicalhaving 1 to 15 C atoms, where, in addition, one or more CH₂ groups inthis radical may each be replaced, independently of one another, by—C≡C—, —CH═CH—, —(CO)O—, —O(CO)—, —(CO)—, —O—, —NH— or —NR¹— in such away that O and N atoms are not linked directly to one another, n denotes1, 2 or 3, R¹¹ in each case independently denotes a halogenated orunsubstituted alkyl radical having 1 to 15 C atoms, where, in addition,one or more CH₂ groups in this radical may each be replaced,independently of one another, by —C≡C—, —CH═CH—, —(CO)O—, —O(CO)—,—(CO)— or —O— in such a way that O atoms are not linked directly to oneanother, and where two radicals R¹¹ may be linked to one another to forma ring, A¹ and A² each, independently of one another, denote anaromatic, heteroaromatic, alicyclic or heterocyclic group, which mayalso contain fused rings, and which may also be mono- or polysubstitutedby a group L, L in each case, independently of one another, denotes —OH,—(CH₂)_(n1)—OH, F, Cl, Br, I, —CN, —NO₂, —NCO, —NCS, —OCN, —SCN,—C(═O)N(R⁰)₂, —C(═O)R⁰, —N(R⁰)₂, —(CH₂)_(n1)—N(R⁰)₂, in which n1 is 1-4,optionally substituted silyl, optionally substituted aryl or alicyclylhaving 6 to 20 C atoms, or straight-chain or branched alkyl, alkoxy,alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxyhaving 1 to 25 C atoms, in which, in addition, one or more H atoms maybe replaced by F or Cl, Z² in each case, independently of one another,denotes a single bond, —O—, —S—, —CO—, —CO—O—, —OCO—, —O—CO—O—, —OCH₂—,—CH₂O—, —SCH₂—, —CH₂S—, —CF₂O—, —OCF₂—, —CF₂S—, —SCF₂—, —(CH₂)_(n1)—, inwhich n1 is 1, 3 or 4, —CF₂CH₂—, —CH₂CF₂—, —(CF₂)_(n1)—, in which n1 is1-4, —CH═CH—, —CF═CF—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH— or CR⁰R⁰⁰, R⁰ andR⁰⁰ each, independently of one another, denote H or alkyl having 1 to 12C atoms, R¹ denotes H, halogen, straight-chain, branched or cyclic alkylhaving 1 to 25 C atoms, in which, in addition, one or more non-adjacentCH₂ groups may be replaced by —NR₂, —NR—, —0—, —S—, —CO—, —CO—O—,—O—CO—, —O—CO—O— in such a way that O and/or S atoms are not linkeddirectly to one another, and in which, in addition, one or more H atomsmay be replaced by F or Cl, and m1 denotes 2, 3 or
 4. 20. A compoundaccording to claim 19, wherein m1 denotes 2 or 3, and A¹ and A²independently denote 1,4-phenylene or cyclohexane-1,4-diyl.
 21. A methodfor effecting homeotropic alignment with respect to a surface delimitingan LC medium, said method comprising adding at least one organiccompound containing at least one polar anchor group and at least onering group, according to claim 1, as an additive for said LC media. 22.A process for the production of an LC display comprising an LC cellhaving two substrates and at least two electrodes, where at least onesubstrate is transparent to light and at least one substrate has one ortwo electrodes, comprising: filling of the cell with an LC mediumcomprising a low-molecular-weight liquid-crystalline component, apolymerizable component and an organic compound containing at least onepolar anchor group according to claim 1 which is suitable for effectinghomeotropic (vertical) alignment of the LC medium with respect to thesubstrate surfaces, and optionally polymerization of the polymerizablecomponent, optionally with application of a voltage to the cell or underthe action of an electric field.
 23. The liquid crystalline mediumaccording to claim 11, wherein the saturated, partially unsaturated orfully unsaturated, optionally substituted polycyclic radicals having 5to 20 cyclic C atoms, one or more of which may be replaced byheteroatoms, are bicyclo[1.1.1]pentane-1,3-diyl,bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl,

where, in addition, one or more H atoms in these radicals may bereplaced by L, and/or one or more double bonds may be replaced by singlebonds, and/or one or more CH groups may be replaced by N, R⁰, R⁰⁰ each,independently of one another, denote H, F or straight-chain or branchedalkyl having 1 to 12 C atoms, in which, in addition, one or more H atomsmay be replaced by F, M denotes —O—, —S—, —CH₂—, —CHY¹— or —CY¹Y²—, andY¹ and Y² each, independently of one another, have one of the meaningsindicated above for R⁰ or denote Cl or CN.
 24. The liquid crystallinemedium according to claim 1, wherein the polar anchor group is H,halogen, straight-chain, branched or cyclic alkyl having 1 to 25 Catoms, in which, in addition, one or more non-adjacent CH₂ groups may bereplaced by —NR⁰—, —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— in such away that N, O and/or S atoms are not linked directly to one another, andin which, in addition, one or more tertiary carbon atoms (CH groups) maybe replaced by N, and in which, in addition, one or more H atoms may bereplaced by F or Cl, with the proviso that at least the radical R²contains one or more heteroatoms selected from N, S and/or O.
 25. Theliquid crystalline medium according to claim 24, wherein the polaranchor group is —(CH₂)_(n)—OH or —O—(CH₂)_(n)—OH, and n is 1-11.
 26. Theliquid crystalline medium according to claim 1, further comprising oneor more compounds of the formula A, B or C,

in which R^(2A), R^(2B) and R^(2C) each, independently of one another,denote H, an alkyl radical having up to 15 C atoms which isunsubstituted, monosubstituted by CN or CF₃ or at least monosubstitutedby halogen, where, in addition, one or more CH₂ groups in these radicalsmay be replaced by —O—, —S—,

—C≡C—, —CF₂O—, —OCF₂—, —OC—O— or —O—CO— in such a way that O atoms arenot linked directly to one another, L¹⁻⁴ each, independently of oneanother, denote F, Cl, CF₃ or CHF₂, Z² and Z^(2′) each, independently ofone another, denote a single bond, —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—,—CH₂O—, —OCH₂—, —COO—, —OCO—, —C₂F₄—, —CF═CF—, —CH═CHCH₂O—, p denotes 1or 2, q denotes 0 or 1, and v denotes 1 to
 6. 27. The liquid crystallinemedium according to claim 1, further comprising one or more compounds offormula ZK

in which the individual radicals have the following meanings:

R³ and R⁴ each, independently of one another, denote alkyl having 1 to12 C atoms, in which, in addition, one or two non-adjacent CH₂ groupsmay be replaced by —O—, —CH═CH—, —CO—, —O—CO— or —CO—O— in such a waythat O atoms are not linked directly to one another, Z^(y) denotes—CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —CO—O—, —O—CO—,—C₂F₄—, —CF═CF—, —CH═CH—CH₂O— or a single bond.